Abstract: To meet the static calibration requirement of the balances used in force tests of 2 meter scale high speed wind tunnel,a 70kN strain gauge balance calibration system is developed. Based on the traditional OFAT method,the scheme for four degree of freedom,balance body ax-is system replacement and automatic calibration is adopted.Standard weights are applied to pro-vide accurate calibration loads by using automatic loading weights device,which controls weights independently.Through the double cross hinge force acting point positioning device and the but-terfly shape load-adapter,balance can be loaded exactly.Gapless replacement transmission mech-anism ensures precise replacement of the balance.The final calibration system can meet the cali-bration requirements of different types of balances such as sting and ring ranging from 20kN to 70kN loading.