Abstract: Thermal and irradiation would result in the formation of Cr enriched α’ phase in ferritic steels. The Cr precipitates can impede the mobility of dislocation, causing material hardening and embrittlement. Knowing the interaction mechanism between dislocation and Cr precipitates can help understand the irradiation hardening of ferritic steels. Using molecular dynamics（MD）, the interaction between Cr precipitates and edge dislocation（ED） in BCC-Fe system was studied; the effects of precipitate size, Cr content in precipitate and cutting position on the pinning strength of Cr precipitate were estimated. The results show that: dislocation shear the Cr precipitate leaving no defects; the pinning strength increases with the size of Cr precipitate; Cr precipitate with higher Cr content is a stronger obstacle for dislocation; it shows highest CRSS when dislocation cutting along the equator plane of Cr precipitate.