Abstract: Reinforced concrete space frames have cracks under normal service condition. A reasonable analysis must consider nonlinearity due to cracking. Based on the finite element analysis of member structures and the generalized stress-strain relation of member section, a grid-equivalent section method is put forward to perform nonlinear analysis of space frame structures. Factors including material nonlinearity, effective member stiffness degradation induced by concrete cracking, concrete creep and loading course are considered. The corresponding implementation procedures are given in the paper, and the program is coded by hybrid programming method. Partial functions of ANSYS are used. Computational results of two frames verify the program and the accuracy of results is satisfactory. A super-long frame structure subjected to load and temperature is also studied.