The majority of surveys often cannot be evaluated due to a lack of actual feedback. However, pre-election polls offer a unique advantage that it can be examined by the final outcome of the election. Through measuring the margin of error from the final vote tally, we can improve the survey methodologies in a wide area of application. Nevertheless, few research has focused on a assessing Taiwan's pre-election poll performance in the past. In Taiwan, people are becoming more and more interested in and concerned with election campaigns. Before every important election, journalists, pollsters, and political commissions perform dozens of pre-election polls. Therefore, we can have sample size large enough to make quantity analysis now. In this paper, we collected poll results for the 2000 election campaign of Taiwan, R.O.C, where the data was restricted to those groups that have polls published in public. After modified Mitofsky's (1996) and Traugott's (2001) polling accuracy methods and reallocated the "undecided" in polls, the modified method was adopted for evaluating Taiwan's 2000 poll performances. Furthermore, some statistical techniques were used for analyzing seven influential factors, including survey frequency, undecided rate, recommendation organization, conducting status, field days, effective sample size, and days to election in this paper.