The CuW/ZL101A integrated materials were prepared by the solid/liquid diffusion bonding process, the microstructures and formation mechanism of the diffusion solution layer (DSL) were investigated. The results showed that a good bonding interface was obtained at 690-705 ℃ for 60 min. With the growth direction perpendicular to the interface, the interfacial DSL mainly consists of planar DSL, columnar DSL, eutectic DSL. The phase composition was analyzed by SEM and XRD. The microstructure evolution and formation mechanism of the DSL obtained at 705 ℃ for 60 min can be explained as follows: the nucleation occurred at the W-Cu interface, the lateral growth firstly along the interface and the subsequent connection resulted in the formation of the small planar DSL, and then the longitudinal growth resulted in the formation of the columnar DSL. The eutectic DSL consists of lamellar pseudoeutectic and net divorced eutectic structures with the composition closing to or far from the Al-Cu eutectic point. With the increase of bonding time at 690 ℃, the DSL showed the similar morphology but different thickness. In addition, the formation of new phase was not observed.