In high-level waste treatment plants, rooms where the highly radioactive sources (such as the vitrification containers) are operated have high radiation protection risk. On the purpose of ensuring the safety of operators, it is necessary to design corresponding shielding walls, windows and shielding doors to guarantee that the dose rate at the personal operating location outside the room meets corresponding control requirements. Compared with walls, the radiation safety designs of the doors and windows are more complicated. In this article, a shielding door of a hot room inside a high-level waste treatment plant is selected. By means of combing the source characteristics and the source location, the gap between the door and door frame as well as the lap joints of the door and the wall are analyzed in order to characterize the influence factor of the dose rate outside the shielding door. The results illustrate that, under the premise that the shielding design requirements are satisfied, the lap joint between shielding wall and door has a significant impact on the outdoor dose field due to the oblique incidence of the radiation ray. Therefore, in the follow-up design of the radiation shielding door, A certain overlap form of the lap joints between the door and the wall need to be satisfied, furthermore, special attention need to be paid to the shielding of radioactive sources with weak self-shielding effect and strong penetration ability, for ensuring the shielding door to the greatest extent radiation protection ability.