1. A method for calibrating a video camera, comprising: obtaining internal and external parameters of the video camera according to a reference template to calibrate the camera preliminarily, and recording data of a reference object in the same scene with the reference template; and when the video camera needs recalibration, obtaining images of the reference object from at least two perspectives, obtaining the internal and external parameters of the video camera at the time based on the recorded data and the images of the reference object to recalibrate the video camera.