Abstract: To tackle the problem that traditional focus measure technologies cannot measure the focus shifting caused by thermal distortion in single pulse high power laser system, a system, composed with double vertical wedge groups producing array spots, can make instantly focus measure available. Two pairs of wedge-mirror groups which are placed vertically to each other are utilized as beam splitting system in this system. All those rays are finally detected by a detector, and formed a matric of spots with various sizes. Through single detection of spots matrix, various focus position shifts and the focus shifting measurement of the high power laser with single shot are obtained. After theoretical analyzing, software simulating and experiment testing, this technique has the advantages such as the adjustable detecting accuracy and range, good disperse quality, and the ability of restraining the effect of parasitic light.