The invention relates to the field of aerosol measurement, in particular to a full-automatic monitoring instrument for radioactive aerosol. The measurement instrument integrates a sampling device, a sample preparation device, a measurement device and a control unit; the sampling device comprises a filter membrane, a filter membrane storage device, a mechanical transmission mechanism, an intelligent air pump, an aerosol sampling head and a sampling air chamber; the control device is used for automatically controlling sampling, sample preparation and measurement; the sample measurement device is used for measuring a sample; the aerosol sample is quickly, continuously and fully-automatically collected in a radiative environment, the sample is automatically prepared, the gamma dosage rate is automatically measured, and data is automatically acquired, analyzed, stored, processed and transmitted to a database appointed by a user; natural nuclide, medical nuclide, industrial nuclide, artificial nuclide and the like are detected, and the problems of manual sampling, sample preparation, measurement and collection required for a long term are solved. The measurement instrument is high in intelligent degree and simple and convenient to operate, and can save a large amount of manpower and material resources, thereby having a great promotional value.