The study performed an on-site measurement of the spatiotemporal distribution of aerosols at the range of 0.3~10.0 μm， generated during the use of an ultrasonic scaling instrument in the dental treatment. The mass concentration and number of aerosols were monitored within 0.8 m away from the patient's mouth at three vertical heights from the floor， namely 0.8 m （the height of the patients' mouth）， 0.9 m， and 1.1 m （the height of the medical staffs' mouth）. The mean concentration of aerosols in the area within 0.8 m away from the patient's mouth is approximately 300 μg/m3， which is higher than the allowed thresholds in indoor spaces. This concentration is measured when a suction system with an inner diameter of 6 mm is used. Vertically， the medical staff's respiratory zone is less affected by the spattering during the dental treatment. Horizontally， the concentration of aerosols is similar along different directions and the attenuation is not obvious along the distance. Compared with powder jet handpieces， the diameter of aerosols generated by an ultrasonic scaling instrument is mostly less than 1 μm and the initial momentum of aerosols is lower obviously， indicating different levels of pollution risk of aerosols generated by different instruments. The results indicate that the present control measures， including the suction system， are not effective to prevent the spattering of aerosols generated by ultrasonic scaling instruments. New control measures should therefore be developed to limit the high risk of cross-infection in dental hospitals and clinics.