An air-earth (rock)-tunnel system has often been used for building energy saving. A computing model of the air-earth (rock) heat exchanger is necessary to predict the thermal performance. A numerical simulating model has been developed for the deeply buried air-earth (rock)-tunnel system, in which a 1-D implicit transient convection-diffusion sub-model describes the air temperature and humidity, and a 1-D transient explicit heat conduction sub-model computes the rock temperature. Based on an appropriate discrete scheme, a sequential computing algorithm has been given for solving the air sub-model and the rock sub-model respectively. The accuracy of this numerical model has been verified by comparisons of temperatures of the air and rock and the relative humidity between numerical results and the test data. (C) 2012 Elsevier B.V. All rights reserved.