By comparing the similarity of diffusion equation and the Schrödinger equation,the paper addresses the time-reversal invariance of the physical equations.Although the diffusion of a quantum wavepacket exhibits the same characteristics as the classical particles,it is essentially different.The diffusive matter wave remains diffuse e-ven though the time is reversed while the time-reversal invariance holds.As two wavepackets overlap,it reveals the phenomenon of interference.