Large structures weighing system is upgrading the structure simultaneously using several jacks. After structure leaves the ground, the hydraulic control check valve is used for hydraulic lock, and pressure sensor that under each jack measures the jack cavity pressure. Data is collected by PLC system to obtain the force situation of each jack. With the moment of inertia calculation, center of gravity coordinates of the plane is obtained, the weighing system involves in the hydraulic system, control system, data acquisition and transmission. As the jack wall friction and the leakage factors, in the measuring process, pressure sensor reflects little, and measurement errors appear. In this research, experimental research data has been used to obtain empirical formula under varying pressures, error has also been corrected in weighing measurement system in order to get high precision weighing data. The results are in good agreement after comparing this theory with results measured by weight sensor.