Bioaerosol is commonly present indoors, which may affect human health. In this study, the feasibility of water-soluble chitosan as a biochemical environment protestant to remove bioaerosol from the outpatient clinic was evaluated. Results indicated the predominant bacteria existed in the outpatient clinic included Klebsiella pneumoniae, Bacillus amyloliquefaciens, Corynebacterium callunae, Bacillus cereus and Moraxella sp. The minimum inhibitory concentration (MIC) and inhibition zone of water-soluble chitosan against these strains ranged from 3500-6500 ppm and 2-6 mm, respectively. When the vaporized water-soluble chitosan (500-4000 ppm) was applied in removing bioaerosol from the outpatient clinic, >90% efficiency was achieved at 50 ml/h after 4 h treatment. However, the bioaerosol removal was also attained to 90% after 50 h continuous treatment by a diluted water-soluble chitosan solution (100 ppm). Based on the cost and efficiency consideration, the bioaerosol reduction using a diluted water-soluble chitosan solution for a long-term treatment was practical. These results clearly illustrated that water-soluble chitosan has a great potential as a biochemical environment protestant to remove bioaerosol.