For the purpose of effectually utilizing untreated sewage heat pump for heating and air conditioning,it needs to know the effect of untreated sewage source heat pump on biochemical sewage treatment.The temperature of untreated sewage and the increased electricity consumption of sewage treatment plants for lowering the sewage temperature were investigated,and the relation between sewage temperature and effects of biochemical sewage treatment and the extent of the temperature lowered by pump system were analyzed.The electricity consumption of sewage treatment plants was calculated through an engineering example.The results showed that,when sewage temperature is too low,it was good to use cold-adapted microorganisms for biochemical sewage treatment,and a small quantity of electricity consumption(0.003～0.007 5)kWh/(℃·t)is used.About 0.01 kWh/t quantity of electricity consumption would be used when heat pump system was exploited,which was only 0.6% of the quantity of electricity consumption of pump system.The effect of untreated sewage source heat pump on biochemical sewage treatment is very small.