棒球球路變化是因為球的直行速度和球轉速之間的關係，而產生不同的空氣動力行為並對球的行徑路線產生偏移的變化。以現在投手的水準所能投出的棒球球速約160km/hr和35 rad/sec的自旋速率。要了解這些球路徑的變化就必須要對球所受的空氣動力深入研究。本文是利用數值模擬的方法來探討棒球縫線對棒球整體風阻係數的影響。研究結果顯示：隨著縫線的高度加高，風阻係數也隨著些微變大。另外，縫線在球體直徑為7.4公分時，以時速157km/hr 左右對於降低風阻有顯的效果。

The variety of the baseball’s path is caused by the relationship between linear and spin velocity. It produced different aerodynamic behavior and the variety of path’s offset. For the level of pitcher’s performance the ball’s linear and spin velocity are about 160km/hr and 35 rad/sec. In order to understand the path’s variety, it is necessary to deeply study the ball’s aerodynamic. This study utilized the numerical simulation method to probe the effect of baseball surface seam on drag coefficient. The result is showed that he higher the baseball surface seam’s height the larger the drag coefficient. In addition, the baseball surface seam has the obviously effect of reduce the drag while the ball (redius is 7.4cm) velocity is up to 157km/hr.