Research of variational curve model in limited restriction condition and application in rail train control track database was studied in this paper, raised the method, model and algorithm for digital track map auto-generation from GPS track data, through lots of testify, comparison and improvement using practical data between those algorithm and method, aim at track data, construct mathematical model of data reduction, analyze the limited restriction condition of practical train operation situation, and studied the curve evolution theory, using the algorithm base on variational curve model evolution theory to realize data reduction and error deletion, obtain a few key data automatically to describe rail track in a certain satisfactory error condition, improve the track database automatic generation and optimization method, realize real-time and precise positioning of rail control system base on GPS.