The invention discloses a method for treating a mother solution generated in the production of 98 percent imidacloprid raw powder. The method is characterized by comprising the following steps: distilling the mother solution at 85 to 95 DEG C, and recycling a solvent A in the mother solution; cooling residual solution to 50 to 70 DEG C, adding an extraction agent B, and performing the extraction and phase splitting; cooling a water phase obtained in the phase splitting to 5 to 10 DEG C, crystallizing, filtering, and drying to obtain imidazolidine; distilling an oil phase obtained in the phasesplitting at 95 to 100 DEG C, removing an extraction agent B, adding a solvent C into the residual solution, cooling to 5 to 10 DEG C, crystallizing, filtering, and drying to obtain the imidacloprid crude powder. According to the method, imidazolidine and imidacloprid are separately separated from the mother solution, the separation effect is good, and the content is high; and a separation productcan be directly and separately used as reactants to continue the production and can be used as a finished product to prepare the imidacloprid preparation, so that the recycling rate is greatly increased.