The collapse of reinforced concrete frame structure in earthquake caused a large number of casualties and economic losses. In this paper, the THUFIBER based on MSC.Marc finite element software is used to analyze the reinforced concrete frame structure of Beichuan Credit Union, which was completely collapsed during Wenchuan earthquake. The failure modes which were the lower and upper collapses modes were found by dynamic time history analysis. Incremental dynamic analysis was carried out by 22 earthquake records recommended by ATC-63. The results shown that the Collapse Margin Ratio equals to 4.4, the average maximum storey angle equals to 1/22.