Abstract: The maximum likelihood estimation method of extrinsic parameters of video camera and laser radar is proposed. When calculating the rotation matrix for the coordinate transformation of video camera and three-dimensional laser radar,the error of each initial value is taken into consideration,and corresponding weights are assigned to these initial values according to their respective variance,i.e.assigning minor weights to the initial values with major error and major weights to the initial values with minor error,thus to make the effects of various initial values' error on the calibration results consistent with each other.On this basis,the maximum likelihood estimation of rotation matrix will be more accurate.In addition,by establishing the error model,this paper reveals the error transfer principle in the calibration process,providing reference for the further research on the calibration problems.