Among the existing calibration methods for line structured light sensor, the accuracy of calibration points in laser plane has direct influence on the calibration result of line structured light sensor. A new calibration method for line structured light sensor based on planar target is proposed. The proposed approach does not need to calculate the calibration points in laser plane and the extrinsic camera parameters repeatedly. Planar target is moved to capture laser stripe with different directions and compute the vanish points, and then the normal vector of laser plane is calibrated by the way of fitting straight using the vanish lines. After that, distances between each calibration points are computed based on the principle of cross ratio invariance, and the remaining parameters are calculated according to the distances. Considering the influence of error propagation, an optimized objective function is defined with the obtained parameters as initial value. The results of comparative experiment show that the proposed method has higher calibration accuracy, and the root mean square measurement error is 0.0306 mm. Besides that, the calibration process is simple with low computational complexity, and suitable for calibration on spot.