The invention provides a medium phase change inducement-controllable device and testing method for an external characteristic test of a cryogenic pump. In the device, a power system provides power for stable operation of the cryogenic pump; a pipeline system forms a cryogenic liquid circulation loop; a thermal insulation temperature adjusting system ensures that a cryogenic medium in the whole device is not vaporized after absorbing heat from outside and is used for adjusting the temperature of a wall surface of a volute of the cryogenic pump; an in-tank pressure control system is used for controlling pressure in a cryogenic tank so as to control an occurring position of vaporizing; and a data collecting and analyzing system is used for collecting an electric signal and an image signal and analyzing data. By controlling the pressure in the tank, a flow of the cryogenic pump and the temperature of the wall surface of the volute, phase changes under different inducements can be realized, and the occurring positions of the phase changes are judged according to images shot by a high speed camera, such that the external characteristic test of the cryogenic pump under the four conditions of no phase change, the phase change caused by pressure drop in the pump, the phase change caused by a hydraulic loss and the phase change caused by external heat conduction can be conducted.