NOVELTY - Preparing Albendazole (I) involves: thiocyanating 2-nitroaniline (VI) with ammonium thiocyanated in presence of a halogen; alkylating obtained 2-nitro-4-thiocyanoaniline (V) with n-propylbromide in presence of alcoholic solvent and base in absence of phase transfer catalyst; reducing nitro group of the obtained 4-propylthio-2-nitroaniline (III) by reacting aqueous alkali metal sulfide/alkaline metal sulfide; and condensing obtained 4-propylthio-o-phenylenediamine (II) with alkali/alkaline earth metal salt of methylcyano carbamate in presence of an acid.    USE - For preparation of albendazole (claimed) as a antiparasitic drug indicated for the treatment of a variety of worm infestations; for the treatment to prop up testis trematode, cestode, Echinococcus hydatid cyst, trichina or cysticercus worm.    ADVANTAGE - The method is cost-effective method. The method prepares albendazole with broad spectrum anthelmintic, effective against roundworms, tapeworms, and flukes of domestic animals and humans; and is efficient antiparasitic agent that has good result of treatment not only to pinworm, ascarid, hookworm and whipworm in the animal bodies such as pig, ox, sheep. The method avoids the use of phase transfer catalyst as well as an alkali metal cyanide or alkaline metal cyanide to generate 4-propylthio-2-nitroaniline. This minimize the organic material content in effluent, and reduce the production cost significantly. The method uses methanol as solvent for the reduction which reduces the sluggishness and makes the reaction very smooth and fast. The catalytic reduction in presence of a metal catalyst is a green reaction and environment friendly. The method provides distillation of diamine in Agitated Thin Film Evaporator (ATFE) to remove low boiling and high boiling impurities at 170-185 degrees C under high vacuum at 1 mm/Hg. The contact time of diamine in ATFE is very less hence the decomposition of diamine is minimized resulting increase in yield and purity.    DETAILED DESCRIPTION - Preparation of Albendazole (I) involves: thiocyanating 2-nitroaniline (VI) with ammonium thiocyanated in presence of a halogen to obtain 2-nitro-4-thiocyanoaniline (V); alkylating the compound (V) with n-propylbromide in presence of alcoholic solvent and a base in absence of a phase transfer catalyst to obtain 4-propylthio-2-nitroaniline (III); reducing the nitro group of the compound (III) by reacting an aqueous alkali metal sulfide or an alkaline metal sulfide or reducing in presence of a metal catalyst in presence of hydrogen to obtain 4-propylthio-o-phenylenediamine (II); and condensing the compound (II) with alkali or alkaline earth metal salt of methylcyano carbamate in presence of an acid to form Albendazole (I).