<p>The quantitative evaluation of subgrade service performance is one of the key challenges for road construction in cold regions, and is essential to selection and decision of subgrade structure. Based on relevant specifications and literatures, this paper puts forward a deformation-based performance evaluation system for highway subgrade in permafrost regions. Considering that the deterioration of subgrade in permafrost regions is mainly caused by thaw settlement, the study proposes a hydro-thermal-mechanical coupling calculation model for the calculating thaw settlement of highway subgrade in permafrost regions. Based on the proposed evaluation system, deterioration process of service performance for an actual highway subgrade segment located in a permafrost region is calculated and analyzed, and the clear evaluation conclusions and improvement measures are given. Finally, based on the statistical analysis of a large number of literatures, the mapping relationship between permafrost degradation and subgrade stability is summarized, which provides a newly research idea for proposing an evaluation system of service performance for subgrade engineering based on permafrost degradation rate. These research results could provide key technical support for transportation departments to carry out accurately service performance evaluation and subgrade distress prevention of subgrade engineering in permafrost regions.</p>