An analytical study was conducted to develop an effective method for investigating the gap at the corner of the slab caused by the negative temperature gradients. This method considers the principle of minimum potential energy and the determinate curve using quasi-Newton iterative algorithm to estimate the deformation curve in the process of warping. The proposed method predicts well the measured warping displacements of the CRTSⅡ track slab corner in Beijing-Shanghai High Speed Railway. The analysis results also show that the temperature gradients correlate with the warping of the CRTSⅡ slab, and the increment of the foundation coefficient reduces the warping caused by temperature effectively. In addition, the method reducing the gap of the slab was discussed.