The temples of Angkor monuments including Angkor Thom and Bayon in Cambodia and surrounding countries were constructed with sandstone exclusively.They show severely deterioration caused by physical,chemical and biological processes and,among them,the active growth of microorganisms on the sandstone surfaces leading to biodeterioration cannot be ignored,but knowledge on the microbial community and composition of the biofilms on the sandstone is not available from this region.This study investigated the microbial community diversity by examining the fresh and old microbial biofilms of the sandstone bas-relief wall surfaces of the Bayon Temple by analysis of 16S and 18S rRNA gene-PCR amplified sequences.A comparison of the microbial communities between the fresh and old biofilms showed that the bacterial community of old and fresh biofilms was very similar,but the eukaryotic communities were distinctly different between them.This information illustrates the dynamic formation and succession of microbial communities on sandstone in tropic region.