The invention relates to the technical field of automatic control and discloses a railway line quality monitoring method and system. The method comprises the steps of obtaining railway status data; according to the railway status data, determining intensive maintenance kilometers, wherein the intensive maintenance kilometers refer to a kilometer section with defects in a railway line; according to the railway status data and a first threshold value corresponding to the railway status data, determining why the defects exist in the intensive maintenance kilometers. By means of the method and system, the kilometer section with the defects can be found and why the defects exist is determined at the same time, the more comprehensive, reasonable and scientific monitoring of the railway line quality is achieved, high-quality maintenance and repair are provided and the safe operation of a railway is ensured.