Lifting surface divergence plays an important role in static aeroelasticity analysis.Traditional static aeroelasticity analysis of airplane lifting surface makes the root part fixed without considering the influence of rigid mode. According to AC 25.629-1B, divergence may occur for a structural mode or the short period mode. Inertia relief method is studied and used to take rigid mode into account in divergence analysis. The method is used to compute the divergence results of empty airplane and different payload and fuel for certain airplane. Results are compared with that calculated by flutter method and mode method. Furthermore, results of empty airplane are compared with that gotten by SOL 144 of NASTRAN. Comparison shows divergence results with rigid mode are larger and divergence speed decreases with the increase of payload and fuel.