The invention discloses an automatically-regenerative aerosol diffusion drying device. The automatically-regenerative aerosol diffusion drying device comprises an aerosol sample inlet channel, aerosol diffusion drying devices, a gas path temperature and humidity measuring device, a drying and purging gas generating device, and an automatic gas path switching control device. According to the automatically-regenerative aerosol diffusion drying device disclosed by the invention, by automatically switching the two drying devices, a drying agent in the other drying device is regenerated by drying and purging gas while one drying device is used for drying aerosol gas flow; moreover, the two drying devices are automatically switched according to a set relative humidity threshold value of the aerosol gas flow, so that the continuous automatic operation is achieved, the drying agent does not need to be manually replaced, and the measurement does not need interruption.