Rocket sled test track is a large ground dynamic simulating test facility. It is used for the tudy of solving technical problems that occurred to the testing articles during their operations at high speed and high acceleration in the sky. The constructional key point of the track is the track´s relative linearity precision of one millionth. A stable track foundation, high linearity base line and smooth and surface bright rails are the foundamental conditions for the track. It needs also many new technologies, such as the specially machined rails, rail welding techniques, supersonic flaw detecting for welding, prestress tie-down of the track, straightness alignment, etc. China has successfully built the world ´s only track —XB high accuracy rocket sled test track, of which the rails are specially machined and then welded continuously. This paper describes the background, design approach, technical plan, measurement data, applications, future prospects as well as the technical and constructional characteristics of the track. It indicates the linearity of the track has reached advanced world level.