Due to most of recycled aggregate (RA) possesses higher water absorption, therefore, the process of mixing recycled aggregate concrete (RAC) is more complex than that of normal aggregate concrete (NAC). In this paper, an organosilicone modifier was used to modify RA to reduce its water absorption. Four mixes of concrete were made up with modified RA at a concentration of 1:1, modified RA at a concentration of 1:2, unmodified RA, and NA, respectively. The water absorption unmodified RA and modified RA was compared, and effect of RA surface modification on the microstructure of the interfacial transition zone (ITZ) between the RA and the hardened cement paste was examined. The investigation results show that a higher concentration of modifier is more effective in reducing the water absorption of RA; and there is an optimal value of modifier concentration, and the use of in high concentrations modifier will adversely affect the integrity of interfacial zone.