The invention provides a hierarchical structure based wireless sensor network time synchronization method. According to the hierarchical structure based wireless sensor network time synchronization method, gateway nodes and aggregation nodes are distributed in a monitoring site in advance and sensor nodes are carried by operators; the gateway nodes send hierarchy establishment broadcast data packages with time stamps; the aggregation nodes and the sensor nodes within the communication distance range extract hierarchy information after receiving the data packages, hierarchies of the aggregation nodes and the sensor nodes are changed by adding one to the current hierarchies, and local clocks are modified according to the time stamps; the gateway nodes are served as global time after network hierarchies are built, the timed polling sends time synchronization data packages to aggregation sub-nodes and the aggregation nodes synchronize the local clock time and the global time through the time synchronization algorithm; the sensor nodes perform time synchronization on the local clocks by intercepting time synchronization mutual data package information. The hierarchical structure based wireless sensor network time synchronization method achieves high accuracy time synchronization and improves the wireless sensor network channel utilization rate and the network life cycle.