Abstract: Through the comparative experiments， the types and dosage of the coagulant for food waste water were studied. The continuous mesophilic anaerobic digestion test was carried out using a UASB reactor， and the effects of anaerobic digestion of the pretreated food waste water and raw water was compared. The results showed that the removal effect of three coagulants on pollutants in raw water was PSAF>PAC> PFS， and the optimal dosage of PSAF was 1.5 g/L. The pretreated food waste water entered the UASB system， the gas yield could reach 0.548 m3/kg when the system load was 10.8 kg/（m3·d）， and the treatment effect was best. If the raw water entered the system directly， the suspended solids and oil would affect the activity of the sludge and caused blockage of the pipeline.