Samples of blue bricks of external wall of Qing Dynasty residence in Fuzhou and Shaowu were collected and their chemical content, crystal composition and microstructure were determined by means of XRD, XRF and SEM. As a result, the relationship between the color of blue bricks and the content and valence state of iron element was verified. The differences of surface roughness and water absorption between different bricks were mainly caused by the differences of sintering temperature and amorphous aluminum silicate content.