For the purpose of reducing energy consumption by summer air conditioning and utilizing renewable resources, this paper presents a new type of soil cool storage system with seasonal natural cold source In the cool storage system, the natural cool energy is stored in soil by ground heat exchanger during the cold season and is extracted for space cooling in the summer. Based on film moisture migration theory, a moisture-heat transfer coupling mathematical model is brought up to describe the charging and discharging processes of freeze-thaw phase change of the soil. Besides, a new method is presented that variable time step size is used to solve nonlinear phase change problems numerically. Moreover, a comparison of the model predictions and experimental data shows that the model has good prediction accuracy. The parametric studies indicate that the soil cool storage system full meets the air conditioning needs and has excellence in economic performance. The research results prove that the feasibility of inter-seasonal cool storage system using shallow soil in severe cold regions. (C) 2013 Elsevier B.V. All rights reserved.