Bioaerosol samples were collected in Qingdao coastal region during July 2009 - June 2010 to investigate the concentration and community diversity of microbes in bioaerosols. Microbe concentrations (bacteria and fungi) in marine and terrestrial bioaerosols were determined and diversity indices including Shannon-Weiner index, Simpson's index and Pielou index were calculated in this study. Monthly average concentrations of terrestrial bacteria, marine bacteria, terrestrial fungi and marine fungi were in the ranges of 12-436 CFU x m(-3), 25-561 CFU x m(-3), 0-817 CFU x m(-3) and 11-1346 CFU x m(-3), respectively. There were consistent seasonal variations of these four types of microbe, with higher concentrations in spring and summer and lowest during winter, especially in February. Compared to terrestrial microbes, marine microbes account for higher proportion to the total culturable microbes, with a percentage of 63%. The number of microbial species varied from 17 to 102, and was partially correlated with microbial concentrations, however, it did not show obvious seasonal variation. Based on the analysis of calculated diversity indices, we found that the community diversities of four types of microbe were much higher in January, November and May than in February. The community diversity varied with the season, space and different microbial species, and showed a different seasonal variation from the microbial concentration.