Abstract: To further enhance the detection coverage ability and defect visualization ability of the ultrasonic inspection system for on-site rail welded joints, a high-speed railway rail ultrasonic test system with multiple probe scanning mode and defect display mode has been proposed in this work. The scanning system combines the single probe scanning mode, tandem scanning mode and K-type scanning mode, addressing the problem of missing detection caused by insufficient coverage area of rail detection. The system software with B-type, D-type and C-type view displays was developed to present the defect information from the front, side and top-down perspectives, realizing the high-precision location and quantification of area defects within rail welds. Utilizing this detection system, the results show that the proposed system can achieve a scanning speed of 10 km/h with a scanning accuracy of 2 mm. The quantitative error of area type defect is less than 1 mm, and the location error is less than 2mm. Consequently, the proposed system has successfully achieved high-precision quantification and location of area-type defects in rail welds.