According to the geometric characters of inclined circular plane,a novel rapid diameter measuring system integrating three-dimensional (3D) laser scanning technologies and virtual environm ents is proposed in this paper.In this system,an approach based on the concepts of end points is firstly used to control the view angle and scanning de pth of portable laser scanner.Then,the virtual measurement datum planes are esta blished by online following the scanning trajectory step-by-step,as well as reference to primary datum.Thus,the relative displacements along three o rthogonal directions can be determined between marked end point and virtual measurement datum planes,which directs the scanner to move to the next position.Consequently, high-quality sampling of critical surface area can be automatically performed. On the other hand,the positions of end points are identified and located accordi ng to their height features.Finally,the diameter of inclined circular plane can be obtained by using space projection theory and least square method.The experiments on d ifferent inclining circular planes (55±5mm) were carried out to determine the accuracy and reliability of measuring system.The e xperimental results indicate that a inclined circular plane with a diameter about 55mm is perfectly measured in only 3s with the reso lution less than 0.005mm and the measuring precision over 0.020mm.According to the actual operation results,this proposed measuring system is has high automation and high efficiency,and can be well acceptable for application as on line diameter detection for inclined circular plane in industrial production.