The utility model discloses a roof photovoltaic module fixing device, a mounting bracket comprises a bottom connecting seat, a main support frame and a rotary adjusting rod, the rotary adjusting rod is connected with an adjusting device, the upper end of a photovoltaic mounting plate is connected to the main support frame, the upper end of the adjusting device is connected to the lower end of the photovoltaic mounting plate, and the upper end of the adjusting device is connected to the lower end of the photovoltaic mounting plate. A plurality of photovoltaic panels are arrayed on the photovoltaic mounting plate; the two ends of the rotary adjusting rod are rotationally connected to the bottom connecting bases respectively, a rotary adjusting hand wheel and a rotary locking device are arranged at one end of the rotary adjusting rod, the adjusting device comprises an adjusting connecting rod and a sliding rod, a corresponding adjusting guide rod is arranged at the bottom of the photovoltaic mounting plate, and the sliding rod is clamped in the adjusting guide rod in a sliding mode; the lower end of the adjusting connecting rod is connected to the rotating adjusting rod, and the upper end of the adjusting connecting rod is fixed to the sliding rod, so that the problems that an existing roof photovoltaic installation structure is simple, the position of a photovoltaic panel is fixed and inconvenient to adjust, and the photovoltaic panel is prone to being blown by strong wind to fall off are solved.