In this paper, the water quality characteristics of the produced water from Nan 4-8 (weak alkali) and Sanyuan-6 (strong alkali) of Daqing Oilfield are measured. Combining the particle size distribution and morphological characteristics of the produced water, the critical micelle concentration (CMC) theory is used to discuss the stability of the oil displacement water, and the influences of oil displacement agent, temperature, pH value and inorganic salt on the CMC of the produced water are analyzed. The ASP flooding water CMC is much smaller than the flooding water raw water concentration, indicating that a bilayer is formed in ASP water system. The CMC of flooding water is relatively affected by the pH of the system, that is, the alkali in the oil displacing agent can react with the active substances in the crude oil to form organic acid salts, which have a certain hydrophilic and lipophilic activity. The polymer has the properties of a surfactant while increasing the viscosity of the flooding, and is partially hydrolyzed under the action of an alkali to form a polyelectrolyte and promote the formation of a double-electron layer.