This paper attempts to probe into the calcium oscillation behavior in a biological mathematical model, from which the conditions of complete synchronization are derived based on gap-junction. And thus the ranges of coupling strength g are obtained under the ring coupling and the global one for identical cells. It is observed that bigger synchronization threshold is needed for the ring coupling than the global one. In particular, we point out that the unidentical cells require stronger coupling to make the system reach nearly complete synchronization by means of numeric simulation.