The increase of water content in tailings is the key cause of various diseases. In order to study the microscopical mechanism of tailings capillary water transport, an online monitoring capillary water rise test system was developed by itself, which mainly includes distortionless high-definition digital microscope, three-dimensional mobile microscopic observation frame, CAMERA/VIEW PLAY CAP wireless acquisition system and computer. The system is used to carry out the dynamic real-time observation experiment of the capillary water rising process of tailings, analyze the movement trajectory and migration characteristics of the capillary water, and clarify the evolution law of the unsaturated tailings microstructure under the hydraulic path. The results show that: (1)There is a power exponential relationship between the rising height of capillary water and time, and the rising process can be divided into pure inertia stage, viscosity-inertia stage and pure viscosity stage. (2) Capillary absorption is a process of non-uniform water absorption，the water content of the capillary zone decreases with the increase of the height, and its relationship curve shows an inverse "S" shape, the water content varies from 4.15% to 21.3%. (3) Capillary water migration is a dynamic process in both vertical and lateral directions. The most obvious change in the microscopic structure of tailings is the occurrence of water in pores, with the change of the saturation from low to high, the occurrence shows the shape of pendulum, ring cord, capillary and serous liquid bridge. (4)The capillarity of tailings follows the order of macropores, mesopores and micropores to absorb water, most of which occurs in mesopores, the mechanism of ‘in the macropores and mesopores, capillary water increased preferentially' in tailings granular materials is proposed. The research results revealed the internal correlation mechanism of macro and micro capillary mechanics of tailings, clarified the evolution model of the microstructure of tailings during the rise of capillary water, and further clarified the reasons for the macroscopic damage phenomenon of granular materials caused by the development process of tailings particle drying to humidification.