In order to solve the biodegradation，dehydration problem of ordinary polyacrylamide gel under the condition of high temperature and high salt，the composite gel was prepared with the konjac glucomannan（KGM） and poly（acrylamide/ 2-Acrylamido-2-methylpropane sulfonic acid），P（AM/AMPS）for short，as the main agent，xanthan gum as strengthening agent， methenamine and hydroquinone as crosslinking agent，the optimum amount was determined through investigation of the base fluid viscosity and gelling time. The structure of the composite gel was characterized by Fourier transform infrared spectroscopy（FT-IR） and thermogravimetry（TGA），and the gelling strength，temperature resistance and plugging effect of the composite gel were investigated.The results showed that the composite gel had strong temperature and salt resistance，and the gelling time could be adjusted within 120—180 min. It could meet the harsh reservoir environment with the temperature of 130 ℃ and the salinity of 210 g/L，and could maintain long-term stability.When the P（AM/AMPS）dosage was 0.5%，KGM dosage was 0.5%，xanthan gum dosage was 0.3%，ullotropine dosage was 0.5%，hydroquinone dosage was 0.6%，the gelling strength of the composite gel was the largest，the elastic modulus after gelling was 35.233 Pa. After aging for 7 days，the elastic modulus gradually increased to 71.377 Pa. The composite gel had strong plugging performance. When the injection rate was 1 PV，the plugging rate of core with permeability of 800×10^-3 μm² could reach up to 99.11%.