This paper investigates a new TDMA-based MAC, called C-MAC (MAC using Chinese remainder theorem), protocol with low power consumption while maintaining low packet latency for largescale cluster-based WSNs. To offer low power consumption, each node and coordinator to be active and sleep states based on the time-slot schedule of Chinese remainder theorem. To provide low packet latency, our C-MAC protocol provides an adaptive time-slot scheme to distributively and dynamically wake up time slots for the burst data transmission in a duty cycle. Finally, simulation results illustrate our performance achievements to verify that C-MAC performs better than existing TDMAbased MAC protocols, BMA and EMAC, in terms of power consumption and average packet latency.