Abstract: It is necessary to search for the proper ionizing radiation protecting method on operating 125I seeds source interstitial implantation. The monitor results of ionizing radiation for 125I seeds source interstitial implantation during the stages of operation are described. The radiation dose that doctor may suffered under non-protect condition is evaluated. The radiation exposure to operator is 70 μSv for the 40 pills seeds source of 925 MBq total activity during the whole procedure, such as opening the container, checking and installing the 125I seeds source under the 30 cm operating distance and 10 min. It is estimated to operating doctor for one case that the radiation exposure is 184 μSv. Four suggestions of ionizing radiation protection for this kind of operation were made.