Abstract: The capacity of a Mobile User (MU) is analyzed for downlink distributed communication system in multi-cell environment, when MU locates at any position within the cell. Moreover, the closed-form expression of the capacity is derived. Most papers adopt Central Limit Theory (CLT), and the precondition of it is that the interference terms are more enough. If the interference terms are few, the CLT method has defects in system performance analysis. The contribution of the paper is that the constraint condition is relaxed. The interference plus noise is considered as Gaussian noise with fixed variance when adopting CLT. On the contrary, the variance of the interference plus noise is considered as a random variable influenced by transmit power as well as propagation pathloss in the paper. Under the relaxed condition, the system performance is re-analyzed and the repeated-root problem making use of Moment Generation Function (MGF) is overcome. Through theoretical analysis along with numerical simulations, it demonstrates that the proposed analytical method can represent the propagation pathloss effect on interference more accurately. Thus, the whole system performance is improved.