Taking into account of the current challenges of poor injectability and a short gelation period of conventional gel plugging materials，a high-temperature delayed cross-linked polymer plugging agent（PM-1）was developed through a synergistic approach combining free radical polymerization and cross-linking reaction using acrylamide （AA） and 2-acrylamide- 2-methylpropane sulfonic acid （AMPS） as reaction monomers， azobisisobutyronitrile hydrochloride as initiator， and polyethyleneimine and N，N^'-methylenebisacrylamide（MBA）as cross-linking agents. Optimal synthetic conditions for PM-1 were determined via orthogonal and single-factor experiments. The injectability，gelation performance，and plugging efficiency of PM-1 was evaluated，and the delayed cross-linking mechanism of PM-1 at high-temperature was probed. The optimal synthetic conditions for PM-1 was as follows，mass fraction of monomers was 10% and mole ratio of AM to AMPS was 4∶1，polyethyleneimine and N， N^'-methylenebisacrylamide （MBA） dosage was 0.4% and 0.2% ，azobisisobutyronitrile hydrochloride dosage was 0.1% and polymer BRZ dosage was 1.2%. the injectability of the PM-1 was good. After aging for 96 h at the temperature of 130 ℃，PM-1 could still effectively plug sand layers with meth size of 1.7—4 mm and exhibit a pressure-bearing capacity of 6 MPa for 5 mm fractured layers when combined with inert materials to form a composite gel. Intriguingly，the addition of 0.4% polyethyleneimine extended the cross-linking plugging time of PM-1 to about 3—5 h，which was essential to ensure the smooth construction of underground crosslinking gel plugging.