By using diffusion couple made by inlaying, the forming rule of Ti/Cu diffusion-solution zone was researched with different anneal conditions. The microstructure was observed and analysed by means of backscattered electron and secondary electron image. The forming mechanism was researched in the views of diffusion, dissolve and crystalline. The results show that the formation of diffusion-solution zone comes from the solid phase diffusion, dissolve and crystalline of Ti and Cu at different diffusion temperatures for different times. The diffusion-solution zones with different numbers of layer, thickness and structure are formed almost in the Ti/Cu interphase at the same time; the Cu-Ti compound with a relatively lower percent content of Cu and Ti atom is firstly formed; one layer or several layers are formed on earth, which is determined by the concentration distribution of Cu in Ti and Ti in Cu. When the diffusion couple is heated at 700 ℃ for 100 h, the atom diffusion flow is the Cu diffusing into Ti, the Ti hardly diffusing into Cu. Consequently, the other five layers are formed on the Ti body except the Cu4Ti layer on the Cu filaments; the Cu2Ti and Cu3Ti2 as well as the Cu4Ti3 and CuTi phase layers grow with the opposite directions and intervein each other with bamboo shoot shape, showing relatively obvious floating and protruding, otherwise, the Cu4Ti and CuTi2 phase layer grows with a “plane pattern”