Tailings are a key material for damming tailings ponds, and their shear strength is the core mechanical parameter for ensuring the stability of tailings dams. As a key variable, moisture content directly affects the mechanical properties of tailings. In order to reveal the influence of moisture content on shear strength, the shear performance of tailings with moisture contents of 5.131%, 15.00% and 26.324% is studied by combining repeated direct shear experiments and numerical simulation of PPC particle flow, respectively. The results show that:(1) The moisture content has a controlling effect on tailings strength, and the peak strength shows a trend of "first increasing and then decreasing" with the increase of moisture content, reaching the maximum value at 15.00%; (2) Repeated shear causes significant deterioration of strength. The strength of the sample tends to be stable after the fourth shear stage, and the internal friction angle and cohesion show a decreasing trend;(3) Macro-meso analysis reveals that, under high normal stress, the interparticle occlusion is enhanced, which makes the rising section of the shear stress-displacement curve steeper and the peak strength appear faster; under low normal stress, the particles are prone to rolling slippage, while the development of shear stress is relatively gentle. Based on the above laws, an empirical formula for peak shear strength of tailings considering the dual effects of moisture content and normal stress is established to provide key parameter support for the stability evaluation of tailings dams.