Abstract: In order to enhance the experimental ability of the fast critical assembly, the ancillary buildings was extended beside the critical experiment hall, a sample transmission channel was formed in the physical connection position. In order to ensure personnel the safety of radiation, need to screen out channel. Physical design by using the Monte Carlo method for screen door, the boron containing paraffin as neutron shielding material, stainless steel as photon shielding material. In order to ensure the uniform distribution of boron in the paraffin layer, prevent paraffin internal cavities, the stratification technics was adopted to cast screen door. In order to ensure the effective coverage of channel, using a step by step process for installation. The radiation dose monitoring shows, in personnel daily work of the regional annual radiation effective dose was 0.125 mSv, that less than 2 mSv the limit value of construction project management, far less than the 20 mSv the basic standards for protection against ionizing radiation and for the safety of radiation sources, screen door development to meet the design and use requirements.