In practical surveillance applications, methods for multiple camera tracking have to deal with many challenges such as noises and errors in estimating system parameters. In this pa per, we propose a distributed multiple camera tracking system that can track multiple persons in real time under challenging conditions such as inaccuracy from calibration, noises from background and lighting changes. The system combines a network of cameras located around the environment, a central process unit and mobile devices. Experimental results show that our system has already performed well in military training.