The present invention relates to the processing method of 6-(4-amino phenyl)-4, 5-dihydro-5-methyl-3-(2H)-pyridazinone as the intermediate material for levosimendan and pimobendan as cardiac and cerebral vascular diseases medicine. The processing includes the first mixing of 6-(4-amino phenyl)-4, 5-dihydro-5-methyl-3-(2H)-pyridazinone dextroisomer with alkali or acid in 50 %, dissolving with solvent and reflux, evaporation to dry, water washing, and drying to obtain product. The said method can raise material utilization rate and lower product cost, and through four times one racemization and five times of resolution, the accumulated yield may reach 30-40 %, with the single time resolution yield being 8-12 %.