The invention discloses a water-hammer drain tank inlet stand pipe, which is designed for weakening washing force of drained fluid to the tank body of a drain tank and protecting the tank body from being damaged. A diffusion stand pipe and a fluid climbing stand pipe are fixedly arranged at the tank bottom of the drain tank. Bends at the tops of the two stand pipes are connected through a flange. Diffusion holes with diameter which is 0.2 times the diameter of the diffusion stand pipe are uniformly formed in the wall of the diffusion stand pipe. The fluid climbing stand pipe is fixedly arranged on the tank wall of the drain tank through a pipe clamp, a pin, a fixing plate and a reinforcing plate. During working, the drained fluid enters the liquid climbing stand pipe through a horizontal liquid inlet pipe and then vertically rises up and partial pressure head is weakened in the process. After the drained fluid reaches the top end of the liquid climbing stand pipe, the drained fluid vertically falls down along the diffusion stand pipe and is drained from the diffusion holes section by section, so that the impact force of the fluid can be effectively scattered and the impact of water-hammer liquid to the tank body is weakened. The water-hammer drain tank inlet stand pipe has the advantages that the fluid can be controlled by changing the flowing direction of the drained fluid, the washing force of the water-hammer fluid is weakened and the tank body is prevented from being damaged; the connecting structure is simple and the stand pipe is easy to replace and convenient to maintain.