One of the key problems for wireless sensor network (WSN) is the design of medium access control (MAC) protocol, as MAC is the major consumer of sensor energy. TDMA-based MAC protocol is inherently collision free but it has poor scalability. cluster-based TDMA protocol proves to be more scalable than traditional TDMA protocol while it introduces inter-cluster interference problem. A two level TDMA scheduling (TLTS) protocol is presented to solve the problem, in which the first scheduling ensures that neighboring clusters collecting their member's data during different frame in order to avoid inter-cluster interference and the second scheduling schedules members of cluster sending their data to their respective cluster head during different slots to avoid intra-cluster interference. Simulation results show that TLTS performs better than HEED when node density turns higher. TLTS is more practical than HEED which uses CDMA code to avoid inter-cluster interference for deploying large scale WSN.