The γ radiation level, alpha potential energy of thoron and alpha surface contamination level at amantle factory in the east of Zhejiang Province are reported. The measured results show that the additional annual ef-fective dose equivalent absorbed by the worker in some workshops of the factory was higher than 15mSv-management limit. The alpha surface contamination on the workers hands in some workshops was 10 timesmore than the management limit of National Standard (0.04 Bq/cm2). The mantle factorys main danger to body wasinternal irradiation of α rays from thoron aerosol.