A method for treating production wastewater from the preparation of propylene oxide by co-oxidation, wherein the production wastewater comprises a first portion of wastewater having a peroxide content of 2000 mg/L or more and a second portion of wastewater having a peroxide content of 50 mg/L or less, and the method comprises the following steps: pre-subjecting the first portion of wastewater to a catalytic oxidation treatment to remove peroxides therefrom to obtain effluent wastewater; feeding mixed wastewater obtained by mixing the effluent wastewater with the second portion of wastewater into a multi-effect evaporation unit for treatment, wherein the multi-effect evaporation unit comprises: a first rectifying column, configured to rectify the mixed wastewater to concentrate the mixed wastewater to obtain a first overhead material from the top of the first rectifying column and first concentrated wastewater from the bottom of the first rectifying column as a first column kettle liquid; a second rectifying column, configured to rectify the first column kettle liquid from the first rectifying column to further concentrate the first column kettle liquid to obtain a second overhead material from the top of the second rectifying column and second concentrated wastewater from the bottom of the second rectifying column as a second column kettle liquid; and a third rectifying column, configured to rectify the first overhead material from the first rectifying column and the second overhead material from the second rectifying column for oil-water separation to obtain an oil phase from the top of the third rectifying column as a third overhead material and an aqueous phase from the bottom of the third rectifying column as a third column kettle liquid; subjecting the second column kettle liquid to an incineration treatment to obtain a salt residue; and subjecting the third column kettle liquid to a biochemical treatment to remove organic matters therefrom. pre-subjecting the first portion of wastewater to a catalytic oxidation treatment to remove peroxides therefrom to obtain effluent wastewater; feeding mixed wastewater obtained by mixing the effluent wastewater with the second portion of wastewater into a multi-effect evaporation unit for treatment, wherein the multi-effect evaporation unit comprises: a first rectifying column, configured to rectify the mixed wastewater to concentrate the mixed wastewater to obtain a first overhead material from the top of the first rectifying column and first concentrated wastewater from the bottom of the first rectifying column as a first column kettle liquid; a second rectifying column, configured to rectify the first column kettle liquid from the first rectifying column to further concentrate the first column kettle liquid to obtain a second overhead material from the top of the second rectifying column and second concentrated wastewater from the bottom of the second rectifying column as a second column kettle liquid; and a third rectifying column, configured to rectify the first overhead material from the first rectifying column and the second overhead material from the second rectifying column for oil-water separation to obtain an oil phase from the top of the third rectifying column as a third overhead material and an aqueous phase from the bottom of the third rectifying column as a third column kettle liquid; a first rectifying column, configured to rectify the mixed wastewater to concentrate the mixed wastewater to obtain a first overhead material from the top of the first rectifying column and first concentrated wastewater from the bottom of the first rectifying column as a first column kettle liquid; a second rectifying column, configured to rectify the first column kettle liquid from the first rectifying column to further concentrate the first column kettle liquid to obtain a second overhead material from the top of the second rectifying column and second concentrated wastewater from the bottom of the second rectifying column as a second column kettle liquid; and a third rectifying column, configured to rectify the first overhead material from the first rectifying column and the second overhead material from the second rectifying column for oil-water separation to obtain an oil phase from the top of the third rectifying column as a third overhead material and an aqueous phase from the bottom of the third rectifying column as a third column kettle liquid; subjecting the second column kettle liquid to an incineration treatment to obtain a salt residue; and subjecting the third column kettle liquid to a biochemical treatment to remove organic matters therefrom.