The moisture transport character is an important transport properties of cement-based materials, especially under the periodically dry-wet circumstance, that mostly influence the durability of these materials. In this paper, a novel model describing the quantity of moisture in and out the exposed surface of cement mortar under dry-wet cycles is presented. This model could be easily applied to estimate the quantity of water flow in and out the exposed surface of cement-based materials under dry-wet cycles, with necessary input parameters which could be obtained by simple test methods. The calculation program involved in this model could be realized readily. © 2019, The Authors. All rights reserved.