Abstract: To facilitate the maintenance and repair of railways and locate equipment and disease in the map, the Maintenance and Repair Information System of Gan-Quan Railway was selected as an example and inter conversion method between mileage and coordinate was discussed. This article mainly expounded the mathematical model, calculation method and implementation process of conversion, verified the accuracy and reliability of this method with example. The results showed that the conversion method was easy to program and the conversion precision was relatively high. So that it was suitable for the location of equipment and diseases in the railway maintenance and repair.