Building formwork mounting device and mounting method thereof

The invention discloses a building formwork mounting device and a mounting method thereof. The building formwork installation device comprises a positioning cross rod and a moving angle measurer arranged on the positioning cross rod in a sleeving mode. The moving angle measurer comprises a sleeve which sleeves the positioning cross rod and can slide relative to the positioning cross rod, a measuring rod which is installed on the top end face of the sleeve and hinged to the sleeve, and a display device which is installed on the measuring rod and used for displaying the included angle between the measuring rod and the top end face of the sleeve. The two ends of the positioning transverse rod are inserted into the lantern rings on the telescopic fixing rods below the two adjacent building formworks correspondingly. According to the building formwork installation device, the problem that the distance between adjacent formworks is difficult to adjust when the formworks are installed is solved, repeated measurement