The invention provides a guide plug for facilitating cutting of a steel shell. The guide plug is for cutting a to-be-cut steel shell. The guide plate includes a supporting portion used for supportingan upper die for cutting, an opening end guiding section pressing against an inner wall of an opening end of the to-be-cut steel shell, and a body guiding section stretching into a body of the to-be-cut steel shell, wherein the bottom of the body guiding section is provided with a body limit section pressing against an inner wall of a head portion of the to-be-cut steel shell, for the guide plug,the opening end guiding section presses against the inner wall of the opening end of the to-be-cut steel shell, the position of the steel shell is corrected by the body guiding section stretching intothe body in the cutting process. The bottom of the body guiding section is provided with the body limit section, in the cutting process, the opening end guiding section and the body limit section areboth for pressing and limiting the opening end and the head portion of the steel shell, verticality of the guide plug and the to-be-cut steel shell is improved, the swing degree of the steel shell isreduced, swing deviation of the cutting position is reduced, shoulder height difference of the steel shell after cutting is reduced, and cutting quality of the steel shell is improved.