The invention relates to a fractional-bunch energy balance route defining method for a binary-tree-based wireless sensor network. The method adopts a binary-tree structure in a data structure and thebackward sequence traverse of the binary-tree structure, and combines the energy balance mechanism of a sensing-network nodal point to provide the route defining method. During the fractional-bunch network-organized procedure of a wireless sensing network, the energy consumption of the nodal points of the integral wireless sensor network is effectively reduced and balanced, and the existence period of the integral network is prolonged. In the route building stage, according to the energy balance mechanism and the previous circumstance of the nodal point, the probability that the nodal point which has a bigger surplus energy and a less elected times becomes a bunch head is greatly increased, in the T D M A time interval distribution, when a multi-jump communication is made inside the bunch,the member nodal points successively join the bunch head according to the signal intensity, the bunch head builds the binary-tree according to the sequence of the arriving time, and distributes the operation time interval for every nodal point according to the backward sequence traverse of the binary-tree, the minimum communication distance is realized, the energy consumption of the nodal pointswhich have a relevant long distance to the bunch head is effectively reduced. The method of the invention is simpler, and is easy to be realized, thereby being suitable for various application occasions for the wireless sensor network with data as the center.