Abstract: When the results of the pump comprehensive performance test of the auxiliary feedwater system (ASG) of CPR1000 do not satisfy the supervision requirements, the throttle elements in the pipeline system need to be adjusted. This paper gives a brief description of the adjustment principle of the throttling element. The methods of the theoretical calculation of engineering fluid mechanics and computational fluid dynamics (CFD) provide two ways to obtain the adjustment of the throttling element results. The comparison between two analytical methods shows that the theoretical calculation results are consistent with the modeling analysis results. According to the respective characteristics of theoretical calculation and modeling analysis, the most convenient method can be selected according to the actual needs.