The invention discloses a testing device for testing the deflagration to detonation transition performance of propellant powder. The testing device comprises an electric igniter, an end cover, ignition powder, a pressure sensor, a deflagration to detonation transition pipe and charged propellant powder, and further comprises a sleeve, a simulated bullet and a simulated launching pipe. The end cover is a cylinder with a center step through hole in the axial direction, and is connected with the sleeve through threads, the igniter and the ignition powder are arranged in the center through hole of the end cover, the sleeve is a cylinder with an observation slot along a generatrix of the cylinder, the deflagration to detonation transition pipe is arranged in the sleeve, and is compactly filled with the charged propellant powder, and the charged propellant powder is in close contact with the ignition powder. The simulated launching pipe is a cylinder with external threads at one end, and is connected with the sleeve through the threads, and the simulated bullet is arranged in the simulated launching pipe. The error of testing the wave surface-time relation of explosive and powder deflagration and detonation can be reduced, and the simulated launching pipe is closer to a real launching pipe, and can be equivalent to the actual launching environment.