The purpose of this study was to examine the effects of three approaching steps (standing, approach pad steps and approach across steps) on overarm throwing for 7-12 years old boys. Eighty boys aged 7-12 years old were served as participants for this study. Participants were required to practice throwing for 300 times, including three different approaching steps of overarm throwing. The throwing patterns were simultaneously acquired by using a high-speed camera (JVC 9800) with sampling frequencies 120 Hz. The attained data were evaluated using the Burton's amendment (1992) of development sequences for overhand throw. Two-way ANOVA was used to examine the difference of distance and throwing patterns among age and approaching steps. The result were as the followings; 1. The throwing distances of approach pad steps and approach across steps were significantly better than standing for the boys aged at 10 and 12 years old. As for the throwing patterns, the scores of boys aged from 9-12 years old were significantly higher than the boys aged at 7 years old. However the scores among three approaching steps didn’t achieve the differences significantly. It was concluded that the boys aged 10-12 years old could take the advantage of pad steps and approach across steps to make throwing performance better. These results suggest that boys aged from 10-12 years old could be provided with the instruction of approach pad steps and approach across steps for overarm throwing movements, but no need to emphasize the use of the approach across steps.