The drilling wastewater from oil field was treated through chemical coagulation combining with membrane separation and activated carbon adsorption. Four kinds of coagulants, one membrane and four types of activated carbons were investigated. Poly ferric chloride (PFC) was found to be the best one among the four coagulants, and the COD removal efficiency was 95.3% when PFC of 100mL·L^-1and PAM of 10mL·L^-1were added without pH adjustment. The wastewater pretreated by PFC was further treated by a membrane and activated carbons, respectively. It was found that the activated carbon as the second treatment process achieved an expected result, while the membrane separation did not. The activated carbon powder KC-87 reached maximum COD removal efficiency of 75.3% when KC-87 of 3g was added to 1L wastewater after 1h adsorption. With the combined treatment by PFC coagulation and KC0-87 adsorption at the optimal conditions, the total COD removal efficiency reached 97.4%, and the treated wastewater reached the firstclass level of the Integrated Wastewater Discharge Standard.