Abstract: Based on the shear flexible theory , a finite element model was developed to take into account the quadratic warping effect of arbit rary cross-sections of spatial thin-walled composite beams , taking the 9-node plane element to simulate an arbit rary beam cross-section and the 27-node solid element to simulate the quadratic out-of-planewarping displacement . According to the model obtained in this paper , the interrelated spatial composite beams calculating program was written out . The numerical examples show that the analytical model derived in the paper is correct , which can be used in the analysis of complex spatial thin2walled composite beams under several coupling loads.