Abstract: As one of the significant equipment of China Experimental Fast Reactor (CEFR) operation system, the cold trap plays an important role on purifying the coolant sodium and ensuring safety and steady operation of reactor. Currently, the existing cold trap of CEFR has some problems which include the aggradation efficiency of impurity is low, the wire mesh is blocked easily, and the cold trap is replaced frequently and so on, and these problems have a bad influence on the long-term operation of CEFR. The reasons for these problems in the current cold trap including: One is the unreasonable flow route of sodium, which can cause the partial blocking in specific area, and the other is about the density and disposal of wire mesh, which can make the aggradation of impurity easy in exterior area leading to block the flow channel. According to the reasons, a modified project was proposed to improve the aggradation pattern of impurity in terms of structure design and hydraulics, and consequently extend the operation lifetime of cold trap. The modified project as follows: About 1/3 rates of orifices on interior canister were occluded in wire mesh area, and two rows of orifices were drilled on upside support shell, thus improving the velocity distribution. Synchronously, the wire mesh was separated to three areas which were top area, middle area and bottom area respectively, and the different densities of wire mesh were used to different areas to fulfill the requirement that the aggradation pattern of impurity was from bottom to top. Through 3D modeling and numerical analysis to the project, and comparing the results to current cold trap of CEFR, it can be concluded that the modified velocity distribution is more reasonable than before, and the new disposal of the wire mesh can also meet the aggradation requirement of impurity. Further correlative study will be done according to the actual operation condition of CEFR.