Abstract： The BEC in finite-number trapped atoms is investigated in this paper. The results show that the transition temperature is decreased by the finite-number effect, and the interactions between the atoms change the transition temperature, too. The specific heat below the transition point is no longer proportional to T3/2. In addition to the above effects, the distribution of the trapped atoms depend on its number. The repulsive interaction between the atoms also dilute the density of the atoms.