Abstract: An improved geometrically nonlinear analysis method based on corotational formulation is proposed to improve the computation accuracy of nonlinear problems of spatial Timoshenko beam element. The stiffness matrix of the improved spatial beam element is obtained by using the principle of virtual work; The rigid-body rotation matrix of the element in local coordinate system is calculated by using the reverse motion approach in finite particle method; The tangent stiffness matrix of the spatial beam element is obtained according to the transformation and differential relationship of the rotation angle between the global coordinate system and the local coordinate system; A finite element program is made to analyze the geometric nonlinearity of several typical large deformation structures. The results show that the improved method proposed in this paper is correct and has higher accuracy than the traditional corotational formulation.