The present invention is related to an additive for activating platelet. The additive contains calcium ion, antibacterial, anti-oxidant and buffer. The additive is prepared by mixing well the required components at a specific proportion. The additive is easy and quick to use. Moreover, the additive has the function of activating platelet, and thereby is favorable for medical usage of platelet.本發明關於一種用以活化血小板之添加劑。本發明之添加劑包含鈣離子、抗生素、抗氧化劑及緩衝液。將所需成份依特定比例混勻後以即取得前述血漿樣本之添加劑。本發明之添加劑使用上簡便且快速,而所製得之添加劑具有活化血小板之功用,有助於血小板在醫療上之應用。