Abstract: In order to determine the rational length of unit track concrete plate, the numerical simulation method was applied to analyze the stress and strain responses of unit double-block ballastless track with different lengths under train load, transversal and longitudinal loads, temperature force and temperature gradient. On the above basis, minimum reinforcement ratio needed for track concrete plate and crack widths were calculated. A contrast analysis was conducted by combining site observation. The research result shows that a long unit track concrete plate will result in high internal stresses, big plate end displacement and large crack width, as a result, the minimum reinforcement ratio needed will increase. The reasonable length of track concrete plate for unit double-block ballastless track should be less than 8.0 m, while it should be 6.5 m to subgrade sections along the new Lanzhou-Urumchi railway.