The enhanced oil recovery technology of ASG (alkali, surfactant and nitrogen) composite foam and water alternating injection was studied in high temperature and high salinity low permeability reservoir. The ASG foam and water alternating injection experiments were carried out through indoor flooding experiments, and compared with water flooding nitrogen flooding and surfactant flooding. The results show that the enhanced oil recovery of the method adopted by this study is 16.61%, 10.26% and 9.21%, respectively, compared with water flooding, nitrogen flooding and surfactant flooding technology. Experimental study on injection parameters optimization of ASG foam and water alternating injection is carried out, and the parameters such as slug size, injection rate and gas fluid ratio of ASG composite foam are optimized by bench scale displacement test. The results show that under the condition of the same foam injection volume (1.2 times the pore volume), the effect of foam slug injection with 0.4 times pore volume is best. The foam injection rate has an optimum value of 1.5 mL/min. When the injection rate is too low, less foam is produced, gasliquid separation is easy to occur, and the blocking effect is poor. When the injection rate is too high, the size of the bubble is different, and it is easy to cause the bubble to merge, causing the bubble to burst, and at the same time, it is easy to cause the shear defoaming of the foam. When the gas fluid ratio is 3∶1, 2∶1 and 1.5∶1, respectively, the recovery rate is 2.04% higher than that of the single gas fluid ratio.