Abstract: A multi-stage horizontal elutriator includes a flow inlet, a flow outlet, a hollow container that is disposed between said flow inlet and said flow outlet. This hollow container has a guide-in portion, a first parallel plates set, a second parallel plates set, and a guide-out portion. The first plates set is different to the second plates set. So, the aerosol's falling distance can be shortened significantly. The relative culturable ratio and the survival efficiency for bioaerosols are both high. The structure is simple with low cost.