In order to improve the cavity construction rate of SWRH (single-well retreating horizontal) leaching method on Salt Cavern Underground Storage, the influence of water injection direction on fluid migration in the cavity was studied during cavern constructional period through similar model test and numerical calculation. Simulation results show: The concentration of the injected fresh water increases rapidly after contacting the brine in the cavity, when the concentration increases to about 23%, it becomes a slow increase; the upward and downward incidence is beneficial to the construction of rapid cavity, and the vertical downward incidence is beneficial to the construction of larger cavity. The fluid migration law of similar model test is basically consistent with that of numerical simulation, which proves the correctness of the numerical model. Tests found: the fluid in the cavity can be divided into four regions : the plume region, the boundary solution region, the convective diffusion region and the bottom saturation region; Replacing the water injection direction changes the fluid concentration and velocity in the plume region, which in turn affects the height of the boundary solution region. Compared with the horizontal incidence, the vertical upward incidence, the upward and downward incidence, the four directions incidence and the vertical downward incidence boundary dissolution zones increase by 22.2%, 26.9%, 51.1%, 135.6%. Replacing the water injection direction changes the initial downward flow rate of fresh water, which in turn changes the height of the bottom saturation region Compared with the horizontal incidence, the vertical upward incidence, the upward and downward incidence, the four directions incidence and the vertical downward incidence heights are reduced by 0%, 12.9%, 29.9%, 70.1%.