NOVELTY - Method for preparation of 5-ethyl-pyridine-2,3-dicarboxylic acid diethyl ester involves: reacting chloro-diethyl oxaloacetate and 2-ethyl acrolein as raw materials in reaction medium comprising ethanol by using ammonium acetate as nitrogen source to give 5-ethyl-pyridine-2,3-dicarboxylic acid diethyl ester, where quantity in mols of ammonium acetate for chloro-diethyl oxaloacetate is 1.1-2.5 times and quantity of 2-ethyl acrolein to chloro-diethyl oxaloacetate in moles is 1-1.8 times, and reaction temperature is 70-80 degrees C.    USE - For preparation of 5-ethyl-pyridine-2,3-dicarboxylic acid diethyl ester (claimed) which is useful as intermediate for preparation of medicine, pesticide (preferably imazethapyr), and in chemical industry.    ADVANTAGE - Compared with existing technology, preparation of 5-ethyl-pyridine-2,3-dicarboxylic acid diethyl ester by using ammonium acetate as nitrogen source; improves yield, greatly reduces waste production, and part of solvent can be recycled. In method product is obtained as single component in waste water containing inorganic salt, which is filtered to remove salt and dissolved substance in waste water is obtained that is convenient for burning, thus product can be removed completely by simple processing, will not block incinerator, reduces processing difficulty of waste water, reduces pressure on environment, salt obtained after filtering can be dried, and at the same time quality of product obtained is good; whereas by using ammonium sulfamic acid salt as nitrogen source product obtained is not easy to separate in pure form, causes blocking, and has large processing difficulty. Compared with ammonium sulfamic acid, ammonium acetate has wide source, is easy to prepare, has nitrogen atom use rate of 100%, is easy to dissolve in ethanol under heating condition, reaction can be finished in homogeneous state, and reaction yield is high such as can reach to 90%. The process is thus highly efficient, energy saving, environmental friendly, and easy for industrial popularization.