The synchronization of calcium oscillations in coupled hepatocytes has been investigated by the mean-field approach. Results show that, below the critical noise intensity, the synchronization is improved with increasing the noise intensity, while above it, the synchronization disappears. Meanwhile, a critical coupling strength is found, which is a threshold of occurrence of the complete synchronization, and the phenomenon of synchronization without tuning might be exhibited. Furthermore, when external signal is introduced into the coupled system, there exist an optimal frequency and a critical amplitude of external signal, which makes the system display the best synchronization. (C) 2010 Elsevier B.V. All rights reserved.