A tracking scheme based on Probability Hypothetical Density(PHD) filtering is proposed in order to realize the 3D target positions tracking. The scheme consists of two phases, namely single view tracking phase and multi-camera fusion phase. In the former, at each camera at time k, the color observations are obtained and then the Gaussian Mixture Probability Hypothesis Density(GMPHD) filter is utilized to estimate the 2D target locations.In the latter, the set of 2D estimations of targets, which is obtained in the former, is considered as observations for the data fusion phase to estimate the 3D target locations by the GMPHD filter, so as to avoid the data association between observations and states of targets. The experimental results show that the proposed tracking scheme can not only reliably track the 3D target positions,but also handle the shielding problem for targets at each camera.