In the fracturing treatment process of shale gas reservoir with low permeability and low porosity, pH value of fracturing fluid system directly affects the formation and stability effects of fracturing, it also affects the anionic surfactant fracturing fluid a lot in viscosity, surface tension and shale swelling inhibitory. In this paper, by changing the concentration of the anionic surfactant, basic performance changes of fracturing fluid system in different pH conditions are measured. The experiment results indicate that the SDBS viscosity of SDBS fracturing fluid system increases with pH increase first, then decreases, and reaches the maximum when pH is 9. The best ability to reduce surface tension of the system is with pH 5. The expansion volume of the shale increases gradually with the increase of pH, and reaches the largest when pH is 7; along with the further increase of pH value, shale expansion decreases first and then increases, the expansion capacity is the smallest when pH is 9. When the pH value is invariable, SDBS can inhibit the shale expansion most in the state of critical micelle concentration. In this paper, the effect of pH value on the performance of SDBS fracturing fluid is analyzed from the chemical micro point of view, which is beneficial to the optimization of SDBS fracturing fluid system formula.