In wireless sensor networks (WSN), the existing receiver-initiated MAC protocol based on asynchronous duty cycling, is almost using pseudo-random wakeup schedule of neighbor nodes, in predicting the receiving node wakeup time. In dynamic load conditions in the network, this method cannot change the wakeup interval of node dynamically, thus leading to higher data conflict rates while transmitting and larger data transmission delay. To solve this problem, the paper presents high energy efficiency and low delay MAC (HELD-MAC ), a new protocol that can ensure a different wakeup time between the nodes and predicate the wakeup time of receiving node accurately. The protocol can change the wakeup interval of node dynamically according to the load conditions. Meanwhile, in order to alleviate the problem of energy hole, the protocol can adaptively change the lowest node wakeup interval according to the residual energy of the node. The simulation show that, the HELD -MAC protocol has obvious advantages in the performance of data transmission delay, power consumption, network throughput and transmission collision, compared with RI -MAC and PW-MAC protocols.