Abstract: The injection-production alternation of gas reservoir-type gas storage leads to caprock deformation and pore pressure change, which further results in different degrees of dynamic changes in the geostress field of caprock, thus affecting the mechanical integrity and sealing performance of the caprock. Combined with the principle of effective stress and 3D caprock thin bending plate theory, an analytical model of caprock pore pressure and geostress is established, the results of which are compared with the numerical simulation results, thus verifying the rationality of the analytical model. On this basis, the paper investigates the change law of the caprock stress magnitude and geostress mechanism of S gas storage in China in the depletion-injection-production process. Results show that the farther away from the reservoir, the less obvious the disturbance of pore pressure and geostress is in the caprock, and the stress state of the strata suffering from obvious injection-production disturbance will change in the reverse, strike-slip, and normal fault mechanism. Based on caprock stress analyses, it is concluded that the dynamic mechanical integrity of caprock is in a critical state when the upper limit pressure coefficient of S gas storage is 1.5 (about 18 MPa). Finally, the scheme of multi-condition alternating mechanical test suitable for S gas storage is explored and proposed, thus providing a reference for laboratory tests of similar projects.