The purpose of the empirical research was to explore the effects of the twelve-week martial art fundamental training program on 46 examinees-23 elementary school boys and 23 elementary school girls, who were sampled from the volunteers. By observing the relativity of the twelve-week martial art fundamental training program to the measurement results of the four tests in the flexibility of the 46 elementary school children - 1.modified sit-and-reach test 2.bridge up test 3.shoulder-and-wrist elevation test and 4.front-to-rearsplits test. The author intended to explore the effects of the twelve-week martial art fundamental training program upon one of the elements of human physical strength - the flexibility. The outcome of analyzing the statistics showed a remarkable difference of the measurement of the four abilities of the flexibility between the pre-training period and the post-training period. Significant level was set at α=.05. The findings of the study were as follows: 1. The martial art training in fundamentals was quite effective in improving the flexibility of the school children (P<.05). 2. For the training of the flexibility of the waist and the legs (modified sit-and-reach test), the twelve-week martial art fundamental training program shoed a better effect on the girls than the boys (P<.05). For the training of the flexibility of the shoulders and the wrists (shoulder-and-wrist elevation test), the twelve-week martial art fundamental training program showed a better effect on the boys than the girls (P<.05). 3. For the items of bridge up test and front-to-rear splits test, both the boys and the girls improved their ability after the twelve-week martial art fundamental training program; however, the degree of the improvement doesn't show significant difference (P>.05).