Flat cumulative effect survey device of 222Rn radon daughter radioactive water belongs to radioactivity safety technical field, including sample thief, air pump and flowmeter. The air pump passes through the venthole fixed connection of pipeline and sample thief, flowmeter fixed mounting is on the pipeline that air pump and venthole are connected. The utility model discloses well flat cumulative effect survey device of 222Rn radon daughter radioactive water is small, convenient to use, low in cost, is applicable to the environment investigation under the higher concentration condition in general room and workplace and mine etc. Especially to using due to the daughter of evaluation 222Rn environment investigate of dosage as the purpose. The utility model discloses thereby can reach and obtain the mesh that actual 222Rn daughter radioactive water is flat according to surveying the 222Rn daughter.