The project was for the safe disposal of waste drilling fluid and water reuse. The new technologies developed were featured by integration of physicochemical and microbial enhanced treatment. A series of efficient processing equipment were also developed and used in Changqing Oilfield for oil and gas development. As a result, harmless treatment of waste drilling fluid was achieved and the separated water was reused in the drilling process or environment protection. The safe disposal of waste drilling fluid and water reuse in Changqing Oilfield effectively solved the pollution problem and meanwhile expanded the scale of oil/gas production. The net economic profit in the past 3 years amounted to 300 million RMB.