前言：過肩投擲是人類動作發展的重要參考指標，亦是許多運動的基本要素。在許多球類運動中，如手球、水球、棒球等，都是利用過肩投擲來進行。目的：了解過肩投擲生物力學分析，以做為後續過肩投擲動作研究之參考。方法：以兩部高速攝影機（廠牌型號：CASIO EX-F1高速攝影機，300Hz）收集五年級與六年級參與者各8位之投擲動作的下肢運動學資料，以Kwon3D程式軟體運算，並利用獨立樣本t考驗，比較五、六年級的平均球速與下肢各關節角度之差異性，統計水準定為α＝.05。結果：六年級組平均球速大於五年級組，達顯著差異。五年級組與六年級組在過肩投擲過程中，髖關節、右膝關節、右踝關節及左膝關節角度之平均值，皆未達顯著差異；而左踝關節角度五年級組大於六年級組達顯著差異。

Introduction: The overarm throwing is considered as an important index of development of human actions, it is also the basic elements of many sports. Many games use overarm throwing when playing balls, like handball, water polo and baseball. Purpose: The aim of this study is to understand the biomechanics analysis of overarm throwing, in order to be a reference for a follow-up research. Methods: The author use two high-speed camera (Model: CASIO EX-F1, 300 Hz) and Kwon3D motion analysis system to acquire kinematics data from participants of the fifth grade and sixth grade, each of them is 8. Those research data are using T test (α＝.05) analysis the difference between the average ball speed of fifth grade and sixth grade and lower joint angles. Conclusion: 1. The average ball speed of the sixth grade group were superior to the fifth grade group. 2. There is no significant difference in the average angle of hip joint, right knee joint, right ankle joint and left knee joint between overarm throwing in two groups. 3. The left ankle joint of the fifth grade group is significantly greater than the sixth grade group.