The main gas layers in the Y area of Yanchang Gas Field are the Benxi Formation， Shanxi Formation and Shihezi Formation of the Upper Paleozoic， among which the Benxi Formation had overpressure phenomenon during construction due to the high formation pressure. Incomplete gel breaking after conventional fracturing led to high formation damage due to the high clay mineral content and strong water sensitivity of the Shanxi Formation and Shihezi Formation. In order to solve the problems of water lock， high content of gel breaker residue and high reservoir damage in the Y area of Yanchang Gas Field， a Slickwo online fracturing fluid system has been developed. The slickwo online fracturing fluid system was evaluated in laboratory and field. Laboratory experiments show that the swelling time of the fracturing fluid is 2min， the viscosity is about 50mPa·S at 120℃ for 90min， the anti-swelling rate is 80%， core damage rate less than 15%， and the surface tension of the breaker is 24.35mN/m. The application in the Y area of Yanchang Gas Field shows that the Slickwo online fracturing fluid can meet the requirements of online mixing operation and site sand addition.