During the automatic docking of cylindrical workpieces, it may be necessary to measure the orientation of workpieces accurately without targets. For this reason, a precision scanning method without targets was utilized. The point cloud data was obtained by a laser profile sensor, and the postures were determined by a comprehensive method. Based on Monte-Carlo simulation, the accuracies of the axis fitting method and bus section fitting method were compared, and a new comprehensive method was proposed further. In this study, the pitch angle was obtained by the axis fitting method, the deflection angle was obtained by the bus section fitting method, and the measurement accuracy was significantly improved. In addition, to balance the accuracy and efficiency, the relationship among the number of intercepted ellipses, the number of contour points on each ellipse, and the precision were discussed. Finally, a prototype experiment was conducted to prove the validity and accuracy of the comprehensive method. It is proved that the absolute accuracy of the axis attitude is better than 0.02°, and the standard deviation is less than 0.01°.