Abstract: Environment pollution caused by the drilling fluid is serious and hard to control due to the complicity and variability of mud additives. Large scale of studies and tests are carried out to solve this problem in Jiangsu Oilfield. They use non-toxic mud additives and add chemical fertilizers that contain K+ and NH4+ as inhibitors, which is good for the growing of crops. Tests show that this "green" drilling fluid system has the advantages as strong inhibition, high viscous shearing force and dynamic plastic ratio, and good cuttings transportation.Field using in Well Wei-9 and Wangbei 5 shows its good performances as expected in the design, the cutting recovery ratio reaches as high as 98%, and good hole stability is achieved.