To study the lateral seismic collapse fragility of RC frame structures,multi-record incremental dynamic analysis method is utilized to get the lateral seismic collapse fragility curves of a three-bay and five-storey RC frame building,in which the FEMA-rule and computational non-convergence are taken as a rule of lateral collapse of structures.The results demonstrate that the FEMA-rule is conservative to determine lateral collapse.Under the major earthquake,the structural collapse risk is limited.