1. A visual tracking system, comprising: a sensor unit, for capturing a monitored scene continuously; an image processor unit, coupled to the sensor unit, for detecting when a target enters into the image, extracting characteristics from an image to formulate at least one model of the target, and calculating a matching score of the model; a hybrid tracking algorithm unit, coupled to the image processor unit, for combining the matching score to produce an optimal matching result; a visual probability data association filter, coupled to the hybrid tracking algorithm unit, for receiving the optimal matching result to remove an interference of tracking from a complicated background and output a tracking signal; and an active moving platform, for driving a platform according to the tracking signal to situate the target at the center of an image.