The main transmission route of infectious disease is the dispersion of exhaled particulate matter with pathogen attached on. Therefore, the exploration on the dispersion routine of bio-aerosol is a significant approach for researching control method of indoor infection. Based on the continuous point-source dispersion model, this article puts forward corresponding modified methods according to different airflow patterns and make it become a reasonable predicting tool for the dispersion of bio-aerosol in indoor environment. Such predicting tool is also validated by a bacteria emanating experiment whose results show a notable improvement on predicting accuracy of the modified model. Additionally, the experiment results also indicate that the under floor air supply pattern embraces preferable controlling ability on indoor infections for each occupant in an office environment.