Object. The effects of ATP-introduced a rise in cytosolic free Ca2+ concentration and inhibition of nitric oxide were investigated. Method. Measurement of free Ca2+（[Ca2+] i）of cultured rat tail arterial smooth muscle cells using Fura-2/AM dual excitation wavelength spectrofluorometer. Results. There are two components of [Ca2+] i can be evoked by ATP. One part is Ca2+ entry from Ca2+ channel and formed a plateau. The another part is a peak that released from Ca2+ store. Both of them can be inhibited by NO. Conclusion. The ATP induced [Ca2+] i rise that release Ca2+ from both Insp 3 and ryanochine receptors and Ca2+ entry through calcium channels. The inhibition of NO on ATP induced [Ca2+] i rise that was mediated by cGMP.