We have prepared Na-doped Bi2Sr2CaCu2O8+y(x=0，0.4，0.5, 0.6, 0.7，0.8，1) samples by melting process. The transition temperature of the samples increased up to 90K, and maximum Tc0 achieved was 92.5K. During annealing in flowing oxygen at-mosphere, the Tc of the undoped sample degrade but in the Na-doped sample there is no dramatic Tc change, that indicates their Tc increase have different mechanism. So we believe Na substitution of Bi may destroy the charge balance of BiO layers, the electrons in CuO planes transfer to BiO layers thus create holes in Cu0 planes, the attraction between holes and electrons may be responsible for the superconductivity.