In this study, the microstructure evolution during solution treatment of extruded Al-Zn-Mg profile containing a longitudinal weld seam was firstly reported. The porthole die extrusion experiment was conducted to obtain the extruded profile. The solution treatment was performed at 470 °C for 15 min, 60 min and 120 min, respectively, and the aging was performed at 120 °C for 24 h. The secondary phase distribution, grain morphology, grain size and texture evolution of welding zone during solution were investigated. Moreover, the hardness and tensile properties after aging were analyzed. The results show that the solution for 15 min is sufficient for the dissolution of MgZn2 phase, while Al2CuMg and Al23CuFe4 phases cannot be dissolved even the solution time is prolonged to 120 min. The main texture components of {110}<111> and {110}<115> are formed after extrusion process, and these textures are remained after solution treatment. With increasing solution time, the intensity and volume fraction of texture firstly increases and then decreases. Furthermore, both the average size and aspect ratio of grains in welding zone increase with increasing solution time. The best hardness, tensile strength and elongation was obtained in the Al- Zn-Mg profile after solution treated for 15 min.