The utility model discloses an inner side longitudinal waterproof structure used for a photovoltaic waterproof system, comprising two oppositely arranged profiles used for supporting a laminated member of the photovoltaic waterproof system; a waterproof adhesive tape is clamped on each section bar, and the waterproof adhesive tape comprises an adhesive tape body with a U-shaped cross section; thepressing block mounting piece is connected with the sectional material in a clamping manner and is fixedly connected with the house rafter; and the inner side part water guide piece is connected withthe waterproof adhesive tape in a clamping manner and is used for feeding and discharging water into and out of the inner side of the photovoltaic waterproof system. According to the utility model, after the photovoltaic assembly is installed, the longitudinal waterproofness of the inner side between the assemblies is effectively realized, the waterproofness is not completely blocked, and after the water blocking function fails, the inner side part water guide piece enables water leaked into the system to be effectively guided out, thereby effectively ensuring the beautiful plane of the integrally installed system on the premise of realizing the waterproofness and water guide functions.