The purpose of this study was to explore the relations between mathematics problem-solving strategies and math abilities of elementary school students. Instruments used for this study included Mathematics Achievement Test, The Evaluation of Mathematical Problem-solving Behavior, and three self-constructed mathematics itemes, i. e., "blocks problem", "replacement between high and low level unit problem" and "proportion problem". All these instruments were administrated among 282 sixth-grade students selected from the elementary schools in Chiayi area. The results show that: (1) those ones among correct answers on blocks problem reveal four types of problem-solving strategies; (2) there is significant difference in math abilities among four types of strategies; (3) it is effective to discrminate single and multiple strategies base on children's math abilities; and (4) there are significant relations between various types of strategies and the abilities in solving higher level problem. According to the results, some applications to math problem-solving instruction in elementary schools are also discussed.