The polyvinyl alcohol-epichlorohydrin crosslinked polymer has a problem that the gelation time is short. And the dehydration rate is high and the viscoelasticity is poor under the condition of 130℃ and 22 × 104 mg/L salinity. The crosslinked polymer was modified by adding acrylamide（AM）-2-acrylamide-2-methylpropanesulfonic acid（AMPS）copolymer with different content of AMPS during crosslinking. By measuring the crosslinking time，dehydration rate and energy storage modulus，the preparation condition of the crosslinked polymer was optimized，and the stability and plugging ability of the crosslinked polymer were evaluated. The results showed that the best preparation condition of polyvinyl alcohol-epichlorohydrin crosslinked polymer was obtained as follows：8% polyvinyl alcohol，4% epichlorohydrin，1% AM-AMPS copolymer（AMPS > 70%），3% clay，and 30℃ reaction temperature. The crosslinking time of the modified crosslinked polymer was adjustable in 1—2 h，and the energy storage modulus was greater than 2000 Pa. Under the condition of 130℃ and 22×104 mg/L salinity，it had low dehydration rate and good viscoelasticity. The dehydration rate was less than 10% after polymer was soaked in brine for 90 days，and the viscoelastic coefficient was 0.07. Crosslinked polymer particle had good sealing effect on the crack，and the sealing rate could reach 92.61%. When the ratio of particle size to minimum pore throat diameter was between 1 and 2，the sealing effect of polymer particle was the best. The modified polyvinyl alcohol-epichlorohydrin crosslinked polymer had controllable crosslinking time，strong resistance to temperature and salinity and good viscoelasticity，which could be used for sealing cracks，caves and large channels with high temperature and salinity.