Dissolution, degradation or internal erosion of mineral components in sandy soils may cause loss of soil particles and change the micro-structure of sandy soils, thus affecting the stability of sandy soils as well as the strength and stiffness of soils. As a result, to study the impact of different internal erosion degree on water and sand leakage disaster, a certain number of erodible particles (salts) are introduced to create internal erosion. Under the influence of water penetration, water and sand leakage disaster after internal erosion of sand is simulated, and the test process is simulated and analyzed by PFC3D. The results show that the sand layers with different internal erosion degree have different shapes after test. The results show that with the increase of internal erosion degree from 0% to 30%, the maximum value of sand settlement increases from 3.6 cm to 6.6 cm, and the arching time decreases from 220 s to 140 s. The larger the internal erosion degree is, the steeper and wider the settlement area of soil surface collapse is, the deeper and wider the natural filter channel is, and the more sand loss is. The research results provide important basis for the occurrence mechanism of water and sand leakage disaster in internal eroded sand.