Abstract： Objective To develop an efficiency measurement for bacterial filtration of respiratory filters used in pulmonary function tests to and evaluate its feasibility. Methods An aerosol was generated by jet atomizer using nebulized standard bacterial suspension containing 1.5 × 108 cfu/ml Bacillus subtilis var.niger. The aerosol was driven through three types of commercial respiratory filters. The efferent flow from the filter was collected for bacterial culture and colony count. Bacterial filtration efficiency (BFE) and microbial penetration values (MPV) were computed. Results All the three filters (manufactured by Promed, Cosmed and Microgard) performed a filtration efficiency greater than 99.99% with no significant differences (P＞0.05 ). The microbial penetration values of the three filters were ( 17 ±9), ( 23 ± 12) and ( 13 ±8) respectively.There was no significant difference among the groups, or between Promed filters and the other two types (P＞0.05). Conclusions The use of nebulized bacterial suspension appears feasible to assess the bacterial filtration efficiency of respiratory filters used in pulmonary function test. Homemade filters (Promed) exhibit comparable filtration performance as do imported filters (Microgard and Cosmed) , which meet the requirement for respiratory protective devices and justify their clinical application.