In view of the present situation that there are a lot of waste drilling fluids pollute soil and water in the process of petroleum exploration and development. The drilling fluids in the 5 well fields which is in the north area of Changqing oilfield was choosed to carry on the pollution characteristic analysis. 35 physicochemical indexs and contamination indexes were determined in the drilling fluids. The results show that the waste drilling fluids are ropiness colloid, viscosity high.The drilling fluids’ ingredients are clay, polyacrylamide (PAM) and carboxymethylcellulose (CMC). COD, mineral oils,NH ₄ ⁺,Cr,Cd,Pb,As,pH,chromaticity and so on exceed standard in the drilling fluids,Zn exceeds standard in some individual well fields, the other over-standard parameters’multiple is not big except COD, mineral oils which exceed standard siriously. COD, mineral oils,NH ₄ ⁺and so on are from formation petroleum and the additives such as PAM, CMC etc, high pH is related to calcined soda or caustic soda, Cr、Cd、Pb、As、Zn and so on are from the sidewall material which is cattied by the circulating mud,which are related to formation lithological composition.