In order to deal with the issue that high strength chromium gel always had high crosslinking speed，the formula of plugging agent was optimized by selecting cationic polymer and using of alumina sol. The chromium gel plugging agent suitable for deep profile control was developed and its performance was evaluated. The results showed that for acrylamide （AM）/ acryloyloxyethyltrimethylammonium chloride（DAC）binary copolymer organic chromium gel，the lower the cationic degree，the longer the gelation time was. Alumina sol could effectively delay the gelation time of cationic polymer chromium gel and improve its strength and long-term stability. The optimum formula of chromium gel system was 0.8% polymer Y5 with 5% cationic degree， 0.3% chromium acetate and 0.2% aluminum sol. The gelation time was 55 h at 90℃ and the elastic modulus was 16.6 Pa，which belonged to high-strength gel. The plugging agent had good injection ability and strong shear resistance. Meanwhile，it had strong temperature and salt resistance，and its blocking rate could reach more than 96%. This plugging agent had long gelation time and strong plugging performance，which could satisfy the requirements of deep profile control.