At present, research on the influence of water on the physical properties of rocks is mostly focused on the macroscopic angle. Studies on nanoscale pore structure changes caused by water are few. Shale is characterized by good pore structure and high content of hydrophilic clay minerals susceptible to water. Based on this, in this paper the shale samples were obtained from underground layers 3000 m deep in Songliao Basin, Jilin Province, China. The sample parameters are measured by steam adsorption and nitrogen adsorption experiments under different soaking time conditions. The study shows that the pore structure of shale depends mainly on mineral composition and soaking time. With increase in soaking time, the amount of water vapor adsorption first decreases by 10% and then gradually increases. With water migration in the rock some pore structures are filled with shale particles. As the bubble time increases, the ion diffusion causes development of new pores and micro-cracks, and the adsorbed water vapor amount increases. At the microscopic scale, it is of great practical significance to study the nanoscale pore structure and adsorption characteristics of water vapor in the soft for different soaking time, and to further explore the stress characteristics, adsorption law, and gas migration in shale.