1. An object tracking method for a non-overlapping sensor network, applicable to a sensor network with a plurality of sensors, said method having a training phase and a detection phase, and comprising: in said training phase, obtaining a plurality of measured data through each of said plurality of sensors as training samples; marking out at least an entrance/exit within a measuring range of each of said plurality of sensors; estimating at least three characteristic functions related to an object to be tracked, including sensor spatial correlation function, moving time difference function and appearance similarity function, via an automatic learning method; and in said detection phase, using said at least three characteristic functions as basis for tracking said object and linking relationship of said object.