Thepresent paper presents a design procedure and prototype of detection system, which uses high-precision grating displacement sensor as the main test instrument for detecting bogie wheelset alignment parameters in horizontal plane. Wheelset rim inside distance, wheelbase difference and diagonal difference of newly completed bogie are obtained automatically and accurately in once measurement, moreover, detection is not limited to different bogie wheelbase and different size of wheels. Furthermore, measurement and control system and software are designed; detection results should be saved, queried and printed. The precision of the detecting system could reach to 0.02mm. Compared with foreign similar equipments, the advantages of this detection system is improving the detection accuracy and reducing costs.