[Objective] The influence of different admixtures on the hydrodynamic characteristics of vegetation concrete slope erosion under rainstorm conditions was analyzed to provide a scientific basis for the improvement of vegetation concrete formulations. [Methods] The erosion status of vegetation concrete slopes under four admixed conditions (no additives, polyacrylamide, biochar, palm fiber) with 60° slope and three rainfall intensities (60, 90, 120 mm/h) were analyzed by using outdoor simulated rainfall experiments. The relationship between slope hydrodynamic parameters and soil erosion was analyzed. [Results] The slope Reynolds number was always less than 500, and the slope flow was laminar. The slope Froude number without admixtures was always less than 1 and the slope flow was slow. The slope Froude number with admixtures was always greater than 1 and the slope flow was rapid. The slope surface with external admixture had a larger slope velocity and water flow power, and smaller water flow shear force, runoff depth, and resistance coefficient. The amount of soil erosion on the slope with biochar addition was significantly higher than without biochar addition. The amount of soil erosion on the slope with addition of polyacrylamide and palm fiber was significantly lower than that without addition. [Conclusion] Use of admixtures had a significant effect on the hydrodynamic parameters of a vegetation concrete slope. The amount of soil erosion was very significantly and positively correlated with Reynolds number and water flow power. Adding polyacrylamide and palm fiber can effectively reduce the amount of soil erosion on vegetation concrete slopes, and can be used in the ecological restoration of high and steep slopes.