Abstract: In order to further study the microstructures and essentially understand the characteristics and rules of the recycled brick aggregate porous concrete, during the microscopic studies of the recycled brick aggregate porous concrete, the modern microscopic test equipment-scanning electron microscopy (SEM) is applied to the research of the microstructures of the cement-stone-recycled brick aggregate porous concrete. And according to the assumption of central grains developed by Professor WU Zhong-wei，the authors have analyzed and summarized the structure model for the recycled brick aggregate porous concrete, and have done qualitatively researches of the relationships between the microstructures and the macroscopic strength behavior, and then explored the morphology of ITZ (interface transition zone) and the impacts of aggregates large center mass effect on the macroscopic properties of the recycled brick aggregate porous concrete. Analysis results show that the recycled brick aggregate porous concrete has better interfacial transition zone structure， the structure is very compact and the hydration products are very rich. Water cement ratio, design porosity, maintenance period and permeability reducing admixture all have a certain effect on the compactness of the structure and the type as well as the quantity of the hydration products, and on the strength of the concrete structures. There are a lot of negative center mass effects in the porous concrete and the large center mass is only in the recycled brick aggregate. Studies of the negative center mass effect should be taken as a key issue in the future.