Abstract: To obtain the cavity volume accurately, a calculus algorithm of cavity volume was researched according to data surveyed with a three-dimensional laser scanning system. In the algorithm, the main sectioning axis is fixed first, the model is cut by a group of equally interval parallel planes, and the intersection points are got, so the initial edge contour line is generated by using a convex hull impressed method. Then other intersections within the initial edge contour line are added to the cross-section to form a complete cross-section shape. Finally the volume of the model is got by superposition of the triangular directed area. Experimental results show that the algorithm program is stable and has a higher accuracy, and can be used as an effective algorithm of cavity volume.