According to the characters of large-scale conical workpieces, a novel rapid on-machine geometric measurement system integrating three-dimensional (3D) laser scanning and virtual environments is proposed. In the system, key parts of upper surface of two ends of workpiece are fast captured by two static laser scanners. Vertical and horizontal virtual datum planes are respectively established based on the characters of end planes in order to construct 3D virtual measurement space. The positions of end points are then identified and located by the respect of their height features. Thus, both the center and the diameter of end planes can be obtained by the use of space projection theory and least square method. The height and the taper half-angle can be calculated by the geometric relationship of the center of end planes in 3D measurement space, respectively. The experiments on several typical large-scale conical workpieces are performed. Results indicate that the system can offer the resolution less than 10 μm, measuring precision over 100 μm to the height and the diameter, and it can offer the resolution less than 0.001°, measuring precision over 0.010° to the taper half-angle. According to the actual operation results, this proposed measuring system based on human-computer interaction can be well acceptable for application as on-line geometric detection for large-scale conical workpieces in industrial production.