Abstract: In high temperature and high salinity reservoir, the polymer gel blocking agent has the problems of low strength, poor stability, short gelation time, etc. This paper presents a new blocking agent suitable for this reservoir, which is composed of such a formula as sulfonated tannin (4%~7% in mass fraction), ZY?1 crosslinking agent (1.8%~2.2%), ZY?2 crosslinking agent (1.8%~2.2%), FY?1 stabilizer (1.5%~3.0%) and FY?2 stabilizer (0.04%~0.08%), at 130℃. The gelation time of it is 9~14 h, the gel strength is 0.06~0.08 MPa. The lab experiment indicates that this gel system has better heat resistance, salt tolerance and continuous plugging performances for its volume and strength retention reach over 90%, the plugging rate is still higher than 92%, after 60 days of ageing time in the condition of high temperature (130℃) and high salinity (over 2.0×105 mg/L)