The principle of determining the atomized concentrstion by β-ray tyansndssion measurement is described. The laboratory calibration was carried out with the wet filter paper to simulate wster content in the air

from which the quantitative relation between the β-ray count rate and water content in the air was derived. Therefore

the atomized concentration can be determined by using the β-ray count rate measured in situ and the calibration curve. The tests in still show that the β-ray transmission method used to measure the atomized concentration during the period of flood discharge from the high dam in hydropower stations is precise

rapid and has a higher sensitivity than the γ-ray transmission method.