A novel model of TRAIL-induced apoptosis of Novikoff cells was constructed based on the observation using molecular fluorescence labelling and confocal microscopic techniques. The mechanism of TRAIL-induced apoptosis and the role of Ap5A ［P¹, P⁵-Di（adenosine-5′）pentaphosphate］ during this process was investigatived. The results revealed that: 1) TRAIL-induced apoptosis is both dosage- and time- dependent, which correlates with the remarkable increase of ［Ca²⁺］ in Novikoff cells; 2) Ap5A retards the TRAIL-induced apoptosis as well as down-regulates ［Ca²⁺］ in Novikoff cells. These observations indicate that the mechanism of TRAIL-induced apoptosis and Ap5A retards it through down and up-regulating intracellular calcium concentration respectively.