Abstract: One primary pump trip-residual heat removal by single loop is one of the design basis accident of the pool-type sodium-cooled fast reactor, for which the complicated thermal characteristics deserve to be analyzed in depth. It is difficult to carry out experimental study due to the large dimension of the sodium pool, whereas the numerical method is applicable for the simulation. Therefore, three-dimensional transient numerical simulation of China Experimental Fast Reactor（CEFR） sodium pool in the case of one primary pump trip-residual heat removal by single loop accident is carried out based on computational fluid dynamics（CFD） method. The three-dimensional transient flow, temperature distribution, as well as the key parameters including core outlet temperature, intermediate heat exchanger（IHX） inlet and outlet temperature are obtained under the influence of primary pump coast-down, reverse-flow and asymmetric residual heat removal. The calculated results show that the reverse-flow will develop in the pump and IHXs of the fault loop. Meanwhile, the temperature drops to 394.9 ℃ at 900 second in the core outlet. The temperature of the normal loop in the IHX outlet reaches the maximum value of 360.5 ℃ at around 400 second, and then decreases gradually. The temperature of the failure loop in IHX outlet drops firstly and then rises, which reaches about 364.3 ℃at 900 second. It indicates that the residual heat can be removed by the intact loop to mitigate the accident, so that the overall temperature in the sodium pool can maintain in a relatively low value. It provides important references for the safety analysis of sodium-cooled fast reactor under the one primary pump trip-residual heat removal of single loop accident.