In order to understand how static stretch and PNF stretch affect flexibility improvement of college taekwondo players, the study evaluated the joint working range of the knee joint while testing the jump performance to see if those stretches have any influence on a functional performance. According to the results of the research, each group of the static stretch and PNF stretch was observed with significant improvements in the joint working range and the jump performance. From the comparison between the two groups, only the jump performance came up with significant differences.