Novel polymer-based fracturing fluid was developed to exploit ultra-high temperature reservoirs. SEM and rheology studies suggest that this gel system with rigid spatial network structure could be "healed" by the interaction between polyethylenimine and polymer at high temperature. According to the reaction kinetics, the function of gelling time with temperature was obtained. The viscoelasticity and thixotropy behaviors have been investigated. The maximum temperature that fluid could bear was up to 220 degrees C (170 s(-1)), and up to 260 degrees C (100 s(-1)) after being sheared for 120 min. The shear recovery test indicated that the fluid displayed excellent shear recovery properties at 180 degrees C. The settling rate of proppants and filtration rate of the fluid were 1.401 min/cm and 0.2637 x 10(-5) m/min at 180 degrees C, respectively. The viscosity of the transparent breaking liquid was 2.4 mPa center dot s. Thus, this practical fracturing fluid could be an alternative for the development of oil & gas resources in deep wells.