The invention provides a biochemical treatment method for mixed type chemical fertilizer production wastewater. The method comprises specific steps as follows: after agglomerate floating objects in mixed type wastewater are removed through gratings, the mixed type wastewater enters a water collecting well and is subjected to buffer storage, water distribution, air stripping and homogenization, a coagulant aid and a flocculating agent are added, and then the mixed type wastewater enters a primary aeration pool; an efficient microbial preparation HSBEMBM is added to the primary aeration pool, sodium dihydrogen phosphate is added so as to supplement a nutrient substance P, and toxic and harmful substances inhibiting a denitrifier genus in the mixed type wastewater are removed; effluent of the primary aeration pool automatically flows to a primary sedimentation pool, effluent in the primary sedimentation pool automatically flows to a facultative pool, an aerobic pool and a multifunctional pool for denitrification and decarbonization treatment, and the efficient microbial preparation HSBEMBM is added to the primary aeration pool; effluent of the multifunctional pool flows to a secondary sedimentation pool for mud-water separation, the effluent reaching the standard bypasses a flocculation reaction pool and a final sedimentation pool and enters a clear water pool to be discharged, if the effluent cannot reach the standard, the effluent is treated and pumped into the final sedimentation pool, and effluent of the final sedimentation pool automatically flows to the clear water pool to be discharged or recycled. The wastewater after treatment is recycled to a circulating water system of a factory, the recycling rate is higher than 85%, and the environmental and economic benefits are remarkable.