This research will investigate the importance order and differences of the factors for the participant motivation of the participants swimming across Sun Moon Lake. The result of the research will be provided to the authority as references for designing, arranging the activities in the future. The research method of this study is questionnaire and the objects are the participants swimming across Sun Moon Lake in 2004. The instruments of the research include the participant motivation scale and the SPSS statistic soft ware. There are eight items of the sample background data analysis including sex, age, marriage, whether having children or not, the experiences of swimming across Sun Moon Lake, career, education, and monthly income. The delivered questionnaires are 1000 copies and 532 copies are collected; however there are only 387 valid ones. Because of the research purposes need, the valid questionnaires are dealed with by descriptive statistic, factor analysis, independent sample t-test, one-way ANOVA and Scheffe compare afterward. The results are the importance order of the participant motivation questionnaire there are ability reinforcement, social relationship, the catharsis experience, real benefits. In the different tests there are some found: in different age backgrounds, there are significant differences in real benefits sub-scale. In different marriage backgrounds, there are significant differences in real benefits sub-scale. In whether having children or not backgrounds, there are significant differences in real benefits and catharsis experience sub-scale. In different educational backgrounds, there are significant differences in ability reinforcement sub-scale.