Interferometric parameters calibration is of great significance to get high precision digital elevation model for airborne InSAR system. The physical baseline is one of the important parameters for interferometric calibration. In squinted geometry, the interferometric baseline is not equal to the physical baseline, and it’s influenced by aircraft attitude. The parameter that the traditional sensitivity equations which are derived by differentiating the elevation equation with respect to the interferometric baseline parameter calibrate is the effective baseline, instead of the real physical baseline. Aiming at this problem, this paper analysises the effective baseline in squinted geometry, and formulates the effective interference baseline with the physical baseline and the aircraft attitude, then proposes a method to calibrate the real physical baseline. Finally, A calibration experiment has been performed with real data acquired by the Xband airborne InSAR of the Institute of Electronics, Chinese Academy of Sciences to verify the method.