In order to reveal the effect of polymer sheared by stratum on oilfield output liquid，the electrostatic separation effect of nonionic polyacrylamide（NPAM）after degrading and demulsifier YFPC-792 on W/O emulsion of Brazilian Peregrino oilfield through indoor electrostatic coalescence fast evaluation system was studied. The results showed that YFPC-792 could improve the electrostatic separation effect of W/O emulsion. Under the electric field of 150 Hz and 294.44 kV/m，the best electric field residence time of W/O emulsion was 100 min. With increasing NPAM concentration，the electrostatic separation efficiency and average droplet size of W/O emulsion decreased，and the viscosity of NPAM solution increased. Because of the bridging flocculation effect between NPAM molecules，the electrostatic coalescence effect of emulsion with 200 mg/L NPAM before degrading was the best whose dehydration rate was 81%. While the electrostatic coalescence efficiency of emulsion containing degrading NPAM decreased with increasing NPAM concentration. The electrostatic coalescence efficiency of 20% moisture content emulsion was the worst （49%），while that of 30% moisture content emulsion was the best（81%）. Within 5—15 min after the dehydration of W/O emulsion containing YFPC-792 and degrading NPAM，the W/O emulsion separating effect of gravity sedimentation was better than that of electrostatic separation effect，and then the opposite.