Abstract: In order to maintain and improve the smoothness of railroad tracks, they must be adjusted frequently. Profile fitting is a key step in the adjustment of existing railway lines; the fitting linear of profile determines if track profile adjustment is reasonable and necessary. Circular curve fitting is essential to profile fitting of the existing railway lines. The circular curves on railway profile have short arcs and long radii, which results in difficultlies when fitting accurate curve parameters, in conformity with railway profile linear characteristics. In this paper, we provide a new fitting method applicable to circular curves in railway profiles, according to two characteristics. This method has fewer fitting parameters, and higher fitting accuracy characteristics. In addition, the resulting circular curve parameters meet the profile rail linear requirements, which can provide a reference for existing railway line profile circular curve fitting.