Abstract: Defect cluster-solute complexes induced by high energy neutron during the service of pressurized water reactor pressure vessel (RPV) steel will lead to irradiation hardening and embrittlement, which is the key factor affecting its service life. Using dislocation dynamics method combined with molecular dynamics and molecular statics, the hardening mechanism of copper-rich precipitates in FeCu model alloy was studied. The effects of pinning force and critical angle of unpinning on the calculation results were analyzed, and the confidence level of the calculation results was analyzed. The results show that the unpinning criterion for the precipitates with radius less than 1 nm is mainly force criterion, and it is necessary to accurately calculate the pinning force. The unpinning criterion for the precipitates with radius greater than 1 nm is mainly critical angle criterion, and the critical angle is about 130° for copper-rich precipitates. The results of this study are of great significance for further studying on the irradiation hardening mechanism of RPV steel and predicting the trend of irradiation embrittlement.