A coupling and fixing structure of a panel and a casing of a power supply is provided. The power supply further includes a frame. The casing has an opening and a plurality of raised studs. The casing, the frame and the panel have a plurality of penetrating holes and a plurality of through holes. The frame and the panel have a plurality of positioning holes corresponding to the raised studs. The frame and the panel are engaged with each other and positioned at the opening of the casing through the positioning holes and the raised studs and locked with screws so as to complete the assembly of the panel and the casing. The present invention can strengthen the connection of the panel and the casing, decrease the times of locking, lower the risk of damaging components, and improve the efficiency of disassembly and maintenance.