NOVELTY - A histone deacetylase inhibitor synthesizing method involves adding protected cysteine-1 and threonine methyl ester with condensing agent and organic alkali and reacted to obtain substituted butyric acid methyl ester compound of formula (I). The substituted butyric acid methyl ester compound (I) is reacted with the protected valine, condensing agent and organic alkali to obtain substituted hydroxy butyric acid methyl ester compound (II).    USE - Method for synthesizing histone deacetylase inhibitor.    ADVANTAGE - The method enables synthesizing the histone deacetylase inhibitor in a simple, economic and easy manner with short synthesis route, stable intermediate product and environment protection.    DETAILED DESCRIPTION - A histone deacetylase inhibitor synthesizing method involves adding protected cysteine-1 and threonine methyl ester with condensing agent and organic alkali and reacted to obtain substituted butyric acid methyl ester compound of formula (I). The substituted butyric acid methyl ester compound of formula (I) is reacted with the protected valine, condensing agent and organic alkali to obtain substituted hydroxy butyric acid methyl ester compound of formula (II). The substituted hydroxy butyric acid methyl ester compound of formula (II), p-methanesulfonyl chloride and the organic alkali are reacted with the organic alkali to obtain substituted butyramide compound of formula (III). The substituted butyramide compound of formula (III) is reacted with inorganic alkali to obtain substituted butanoic acid compound of formula (IV). The substituted butanoic acid compound of formula (IV) is subjected to methyl esterification with L-malic acid to obtain 2-hydroxy-succinic acid. The 2-hydroxy-succinic acid is reacted with sodium borohydride and acetic acid solution to obtain substituted pentanone compound of formula (V). The substituted pentanone compound of formula (V) is reacted with tertbutyl dimethylsilyl chloride and organic alkali to obtain substituted hexanone compound of formula (VI). The hexanone compound is reacted with inorganic alkali to obtain the compound acid. The compound acid is reacted with trimethoxy silane, the condensing agent and the organic alkali obtain substituted trimethylsilanyl-ethyl ester compound of formula (VII). The substituted trimethylsilanyl-ethyl ester compound is reacted with camphorsulphonic acid to obtain 4-Hydroxy-3-methyl-butyric acid 2-trimethylsilanyl-ethyl ester compound of formula (VIII) and oxidized to obtain (S)-3-methyl-4-oxo-butyric acid-trimethylsilanyl-ethyl ester compound of formula (IX). The 1-H-tetrazole-5-thiol compound (X), 1-bromo butane compound of formula (X) and the organic alkali are reacted to obtain an intermediate product and oxidized by the oxidizing agent to obtain substituted tetrazole compound of formula (XI). The substituted tetrazole compound is reacted with camphorsulfonic acid to obtain substituted tetrazole sulfonyl compound of formula (XII). The substituted tetrazole sulfonyl compound is reacted with triphenyl methanthiol, triphenylphosphine and condensing agent to obtain substituted tetrazole sulfonyl propanol compound of formula (XIII). The (S)-3-methyl-4-oxo-butyric acid-trimethylsilanyl-ethyl ester compound is reacted with substituted tetrazole sulfonyl propanol compound and the organic alkali to obtain substituted silanyl ethyl ester compound of formula (XIV) is reacted with the camphorsulfonic acid to obtain substituted trimethylsilanyl ethyl ester compound of formula (XV). The amino acid protected by the N-(9-Fluorenylmethoxycarbonyl) (Fmoc), the condensing agent and the organic alkali are reacted to obtain 3-(2,3-dimethyl-butyryloxy)-oct-4-enoic acid 2-trimethylsilanyl-ethyl ester compound of formula (XVI) is reacted with the organic alkali to obtain the free amino compound. The substituted butanoic acid compound, the condensing agent and the organic alkali are reacted to obtain 3-(2-(2-(2-(2,3-dimethyl-1-methylene-butylamino)-3-mercapto-propionylamino)-but-2-enoylamino)-3-methyl-butyryloxy)-oct-4-enoic acid propyl ester compound of formula (XVII). The acid and the organic alkali are reacted to obtain the macrocyclic precursor compound of formula (XVIII). The condensing agent and the organic alkali are reacted to obtain 12-ethyl-6-ethylidene-3-isopropyl-9-mercaptomethyl-14-methylene-16-pent-1-enyl-1-oxa-4,7,10,13-tetraaza-cyclohexadecane-2,5,8,11-tetraone compound of formula (XIX) is reacted with reacted with the iodine to obtain 7-ethylidene-4,21-diisopropyl-2-oxa-12,13-dithia-5,8,20,23-tetraaza-bicyclo(8.7.6)tricos-16-ene-3,6,9,19,22-pentaone compound of formula (XX).