Demulsification dehydration treatment is one of important links in crude oil electric desalting dehydration. Taking SZ 36-1 heavy high acid crude oil as raw material, studied are nonionic demulsifier and additives and analyzed are crude oil emulsion stability and synergistic effect between demulsifier and additives. The analysis results show that small organic molecule additives can change interfacial polarity environment and increase sulfuric acidity to solubilize the asphaltene micelle and destroy the emulsion stability and good synergistic effect can be obtained through combination of demulsifier and additives. Dehydration amount of mixed demulsifier SXF221 is similar to that of same imported ones and water quality after dehydration is better that of imported demulsifiers.