Using strain-gage method for non-root flight load measurement some ground calibration data of 2-spar,3-spar and more than 3-spar airfoil structures with different span-chord ration were investigated where some different-level effects of loading inside strain-gage station have been found. The mechanism of the effect on loading inside strain-gage station was analyzed using3 D structure deformation continuity. Moreover the effects of loading inside station on strain-gage values were analyzed,and virtual load result from loading inside strain-gage station was given and discussed. The results show that airfoil span-chord ratio is an important factor relative with strain quantities when loading inside strain-gage station. For different bending-moment equation of certain airfoil the ratio of virtual loads and applied loads is-24. 1% ,23. 4%,and for different shear equations the ratio of virtual loads and applied loads is-31. 2% ,-,3. 7%.