Abstract: Based on the wire-mesh sensor technology, a novel non-invasive sensor for narrow channel void fraction measurement has been developed, by changing the structure of the wire-mesh sensor (WMS). Through two-phase experiment, the feasibility of this sensor has been verified by compared with high speed camera. In addition, a corresponding post-processor has been developed. To improve the accuracy of the post-processor, based on high speed camera, we evaluate the algorithms used by post-processor. As a result, lanczos interpolation algorithm and Canny edge extraction algorithm were finally selected.