Abstract: In order to discuss the progressive collapse-resistance performance of long-span space structures with an alternate load path method (AP method), a method to evaluate the elements to be removed in the AP method was given. Then the simulation method of elements to be removed was discussed, and the initial condition of a structure before the local damage was considered in an instantaneously unapplied equivalent load method. The numerical example shows that the method is good at considering the initial structural condition and dynamic effect. For a space truss structure, the dynamic increase factor (DIF) for the static analysis of AP method was discussed. It can be concluded that the DIFs of truss structures are smaller than 2.0. However, the value of DIF is close to 2.0 when the middle column of the long side and the corner column are failure. At last, the estimate rule about the progressive collapse of a long-span space structure was discussed.