The treatment of crude oil in Sha'nan oilfield combined station of Zhundong oil production plant is treated by thin oil. With the exploration of heavy oil and Ji 7 dense oil into the system, the quality of the wastewater is changed, so that the wastewater treatment technology and the adaptability of chemical system are changed as well. After treatment, wastewater quality standards are hard to be met. According to the present situation of wastewater treatment system in Sha'nan and the quality of wastewater, the chemical system that can meet the water quality standard of Sha'nan wastewater station is selected. At the same time, the treatment process is optimized and the water quality index of Sha'nan oilfield is met.