An efficient and practical methodology was proposed to realize the path checking: a virtual cylinder was obtained when the transducer was prolonged in the direction of ultrasonic beam, then the path checking was replaced by interference detection between the virtual cylinder and the surface of component. In the interference detection, firstly the surface of component was discretized into many patches presented by bounding box. Secondly the algorithm of orthographic projections was used to detect the collision between the virtual cylinder and bounding box. After that, the patches of the component which interfere with bounding box were subdivided into many quadrangles, finally interference detection between cylinder and quadrangles was conducted so that the accurate results of path checking can be obtained. The influence on algorithm’s performance of choosing bounding boxes was discussed. The results of many experiments show the validity of this method.