Based on the energy conservation of building envelope， this paper takes an internal plastering WSE （Wood fibre、Sepiolite and Expanded perlite） composite moisture control and thermal insulation mortar exterior wall as a research subject and compares it with an ordinary mortar exterior wall for the analysis of moisture absorption and desorption as well as its impact on energy load. Using a thermal and moisture coupling model of building materials from the COMSOL Multiphysics finite element software， this paper analyzes humidity transferring change between ambiance humidity change and exterior walls， as well as the heat transferring mechanism of exterior walls. For the WSE wall， total heat loads and the rate of latent heat loads to total heat loads are investigated in Changsha represented as a typical area with hot summer and cold winter. Besides， the annual energy consumption of the WSE wall is compared and analyzed in Beijing for cold areas and Guangzhou for hot summer and warm winter areas . It was found that velocities of moisture absorption and desorption of the WSE wall outperformed those of the ordinary mortar exterior wall for a long time. Moreover， the WSE wall can conserve annual energy consumption by 22.31% to 23.85% compared with the ordinary mortar exterior. Temperature rise is consistent with the moisture absorption velocity in the process of moisture absorption of walls， which reflects that moisture transfer has a great impact on temperature on the inner surface of walls. The impact is enhanced with the augment of moisture transfer. For the process of moisture desorption of the wall， cooling velocity is faster for the higher moisture desorption velocity. In conclusion， the WSE wall possesses a superior performance on moisture transfer and energy conservation， and it is conducive to the development of the building envelope in energy conservation.