The construction spoil deposits have a unique material composition, and its soil erosion resistance is poor, which is easy to cause water and soil loss owing to rainstorm. Hence, it is important to explore the mechanism of flow reduction and sediment reduction of fine mesh net. To analyze the influence of rainfall duration dynamic changes on flow reduction and sediment reduction benefits of fine mesh net on construction spoil deposits, three rainfall intensities (60~120 mm/h) and four slope gradients (5°~35°) were considered on fine mesh net role of reducing soil erosion on spoil deposits. The results showed that: Under a rainfall intensity of 60 mm/h, covering with the fine mesh net has a significant inhibitory effect on the initial runoff time at 15°~35° (p<0.05), while it can significantly prolong initial runoff time (15°~25°) when a rainfall intensity more than 60 mm/h (p<0.05). There was a significant difference in the sediment reduction benefits of 60 mm/h and 90 mm/h (120 mm/h) rainfall intensity under different slopes (p<0.05). The flow reduction and sediment reduction benefits of fine mesh net were decreased with the prolonging of rainfall duration, and reached the threshold at a rainfall intensity of 90 mm/h. The power function can describe the relationship between the benefits of flow and sediment reduction with the rainfall duration well, and the benefit attenuation coefficient(b) increased sharply with the increase of rainfall intensity. The flow reduction and sediment reduction benefits of fine mesh net cover can be divided into high-efficiency stage, decreasing stage and stable stage with the change of rainfall duration. In general, considering the development of soil and water conservation work in production and construction projects, it is recommended to use temporary cover when a short-duration (< 30 min) and heavy rainfall (< 90 mm/h) is the main rainfall in the construction area of production and construction projects, which can effectively reduce soil erosion. The research results can provide reference for the supervision of soil and water conservation of production and construction projects.