In the past, most scholars emphasized the cause of the short-term and long-term abnormality, but often neglected the influence of measure method. As a result, seldom scholars explained the measure method completely. Most scholars think market factor can explain asset return completely, so they use CAPM to evaluate the short-run and long-run performance of IPOs. They find IPOs have initial abnormal return, but they are underperformance in the long run. But if market factors cannot explain IPOs performance completely, short-run and long-run performance does exist or just the model cannot explain? We think it is necessary to modify three-factor model to improve its explanatory power. We utilize Fama-French three- factor model and momentum factor to assemble into four-factor model to revaluate IPOs performance, explore the reasons which influence abnormal return of IPOs in Taiwan, and discuss market efficiency to understand the tendency and the variation of IPOs performance. We conclude that there is no underperformance in Taiwan and Taiwan¡¦s stock market is market efficient. In addition, the empirical result is the same with Loughran and Ritter¡]2000¡^that it will increase explanatory power to use purging benchmark.