The invention discloses a media access control method for a wireless sensor network, which is applicable to the field of wireless network design; wherein, network nodes are divided into cluster-head nodes and ordinary nodes; an operational process runs in a periodic mode and an operation cycle is divided into four stages, namely a synchronization stage, a data stage, a sleep stage and a request stage; the specific operational process comprises: the ordinary nodes send data traffic and routing information to the cluster-head nodes in the request stage of each cycle; the cluster-head nodes calculate the cycle length and the duty radio and send the cycle length and the duty radio to the ordinary nodes in the synchronization stage of the next cycle; the ordinary nodes receive a synchronization package, set own cycle length and duty radio and update the local time in the synchronization stage, carry out data communication in the data stage and enter a sleep state to reduce power consumption in the sleep stage. The method of the invention effectively solves the problems in the present wireless sensor network, namely the synchronization and the self-adaption of data traffic, reduces the energy consumption of nodes and the delay time of data packages and increases the transmissibility of data packages at the same time.