Absolute measuring principle of the high-speed rail was introduced to the measurement of existing speed rail. The line parameter reconstruction and long-wave smooth management is implemented. CPIII control points are laid along existing speed rail. Using the track fine-adjustment instrument, the center geodetic coordinates of midline of track were measured precisely. By least squares fitting method, parameters of straight line between curves was calculated. Plane curve were reconstructed based on measured geodetic coordinates of the continuous rail. The optimization results were used for the t...