1. A method for camera calibration, the method comprising: detecting moving objects in a video sequence; obtaining tops and bottoms of the detected moving objects; creating straight lines connecting the tops and straight lines connecting the bottoms of the moving objects at different positions as perspective horizontal parallel lines; estimating at least two horizontal vanishing points according to the at least two groups of perspective horizontal parallel lines; defining a horizontal vanishing line by the at least two horizontal vanishing points; and calculating calibration parameters of a camera according to the vanishing points and/or the vanishing line.