The Yanchang oilfield has abundant low permeability reservoirs, and during the well completion process, the liquid invasion is the main factors accounting for the reservoir damage. In order to prevent the working liquid from damaging the reservoir, the perforating fluid for protecting reservoir is developed through modification of xanthan gum XG to get XG-HA as viscosifier by means of microwave method, so as to enhance the apparent viscosity by 80% and shearing up to 27 Pa under salt water of 4% weight. The formula of this perforating fluid is: clean water+0.8% to1.2%XG-HA+5%HFY+0.2%HEC+1% to 2%HCS-G+0.3% to 0.4% 4# surfactant+2% to 5%KCl. The solid free system passed the test, and the results show that the perforating fluid has low API filtration, and the viscous rheology is controlled in 8.2 mL, and cuttings recovery rate up to 91.23%, therefore, it is of high stain resistance and good demulsibility and biodegradation. The dynamic damaging and simulative experiments of core show that the core recovery rate with this perforating fluid system is 88.5%-95.3%. In Yanchang oilfield, the field application results show that, the system can effectively protect the reservoir and easy to be biodegraded, and therefore improving the single well production. This technique is feasible in field and worthy of being promoted.