In order to evaluate the energy saving effect for building outside wall under the damp island environment, the heat insulation performance of brick wall, MU10 concrete brick wall and aerated concrete are tested. The testing method is combined of infrared photos and heat flow meter. The results showed that the insulation performance of clay brick is worst, its heat transfer coefficient is 60% more than that required by energy saving standard. Although the concrete brick has painted 25mm polystyrene granule outside, the heat transfer coefficient is still smaller than energy saving standard required. The economic thickness of polystyrene granule is 79mm , which makes the both heating cost and insulating layer minimum during the life cycle of heat insulating layer. Among the three types of outside wall, only the aerated concrete can satisfy the energy saving standard for hot summer and cold winter district, it constitutes the self-insulating system.