Abstract: Aimed at the stratum feature and ground ecologic environment condition in Jiangsu Oilfield,the anti-sloughing,oil reservoir protection and environmental protection performance of drilling fluid were studied cooperatively.Based on the developing and screening of additives which can meet the environmental protection requirements such as antifriction,fluid loss agent,reservoir protection agent and so on,the environmental friendly and reservoir protection drilling fluid was developed through optimizing formula and properties of which such as anti-sloughing,reservoir protection,slit shut-off capacity and so on were evaluated in doors.The results of field test show that the drilling fluid has good inhibition and anti-sloughing performance,lubricity,reservoir protection effect and easily controlling rheological property.As all kinds of environmental criteria of which arrive at agricultural use pollution criterion,the drilling fluid can be discharged directly and the drilling fluid pollution was controlled from headstream.