【Objective】Fish-scale pits measure is a widespread and typical soil and water conservation engineering measure in Loess Plateau that can be used to impound runoff and reduce the soil erosion mass and create a good water condition for vegetation growth. In order to clarify erosion evolution processes and flow hydraulic characteristics of fish-scale pies measure under the condition of continuous rainfall. 【Method】In this paper, we analysed the erosion evolution with 3D laser scanner and realized graphical and digital process of erosion evolution on fish-scale pies slope by laboratory five rainfalls simulation. 【Result】The results showed that: (1)Dynamic process of fish-scale pits erosion could be presented as splash erosion－sheet erosion－drop pit－rill erosion－longitudinal erosion－headward erosion－collapse. By the end of the 5th rainfall, the largest rill length、width and depth respectively increased to 80 cm、22 cm and 7.8 cm. During the first two rainfalls, fish-scale pits played a significant role in water storage and silt detention, sheet erosion and rill erosion occurred at some parts of slope; Later, due to excessive water of pits and high moisture content of side slope, leading to collapse phenomenon in pits and longitudinal erosion, rill headward erosion at down-slope, also increased erosion. (2) As the rainfall duration increases, the down-slope velocity and runoff depth were increased with fluctuation because the rainfall could be hold up in pits. What’s more, vortex accurred in pits and streams scour accurred in slope surface.The order of the average flow velocity and the average water depth is: the up-slope>mid-slope>down-slope. The velocity and depth in rill were significantly larger the slope. The Reynolds number of up-slope and mid-slope was less than 500, and for down-slope, it was over 500 at the end of 5th rainfall. When rainfall accumulated duration reached 58 min and rainfall increased to 87 mm, erosion increased dramatically. Fish-scale pits unable to played a positive effect. (3) During five rainfalls, the upslope and mid-slope flow regime was laminar flow. With the down-slope pits being filled, slope runoff fluctuated greatly, down-slope flow became turbulent flow from laminar flow and changed between subcritical flow and supercritical flow. (4) Resistance mainly comes from rain, grain and form resistance, and form resistance that orginated from the rugged slope was the dominant resistance. Due to the callapse、scour and fluctuant change of terrain, resistance decreased with rainfall accumulation duration accompanied by minor fluctuations. The order of resistance was form resistance> grain resistance> rain resistance.【Conclusion】The study was of momentous significance to clarify the fish-scale pit slope erosion and its mechanism, also provides theory basis and decision support for loess plateau area to layout fish-scale pits reasonably. Only if we layout fish-scale pits reasonably in Loess Plateau area can we improve and keep soil moisture greatly.