In order to evaluate the effectiveness of existing engineer measures for wide permafrost subgrade in Qinghai-Tibet plateau, a finite element (FE) model of temperature field of permafrost subgrade was first constructed by FE software ABAQUS and the secondary development platform. The temperature fields of normal subgrade, rock embankment, EPS insulation layer subgrade, and composite subgrade were then analyzed and compared with the help of the FE model. Furthermore, the change rules of melting depth for four kinds of subgrades were studied. The results demonstrate that the temperatures of the subgrades with different cooling engineer measures all change periodically over time, but the mean annual temperature rises. Under the same condition, the temperature of composite subgrade is the lowest, and its thermal stability is the best. When the width increases, the melting depth of normal subgrade rises linearly, and the melting depth of rock embankment shows a three-stage rising trend, while for EPS insulation layer subgrade it is a two-stage rising trend. Meanwhile, the melting depth of composite subgrade rises with the increase of the width, but the variation is very small. The mere EPS insulation layer or rock embankment is ineffective, while the insulation-gravel composite subgrade has excellent performances on the cooling effectiveness of wide subgrade in permafrost region.