Abstract: Steel cord core conveyor belt is a traction and carrying component of belt conveyor, and joint failure is the main cause of steel cord core conveyor belt failure. In order to improve the joint strength and vulcanization efficiency of the conveyor belt, this paper proposes a preformed core rubber laying technology based on the existing joint vulcanization process. Taking the ST1 600 steel cord core conveyor belt joint as the research object, the application of this technology is theoretically analyzed and experimentally studied. Firstly, the mechanical model of the conveyor belt joint is established and stress analysis is conducted. The influence of uneven horizontal and vertical spacing of steel cords on the joint strength is studied using ANSYS Workbench software. Then, a preformed core rubber laying method is proposed, and the effect of filling core rubber and triangular, trapezoidal, and semicircular core rubber grooves on limiting the offset of steel cords is compared through fluid-solid coupling analysis of core rubber. Finally, the influence of this technology on the adhesive strength of the conveyor belt, joint vulcanization efficiency, and joint strength is studied through joint preformed core rubber vulcanization experiments. The research shows that the stress of steel cords at the conveyor belt joint is related to their longitudinal displacement. Due to the inability to achieve uniform distribution of steel cords in traditional joint vulcanization operations, uneven stress of steel cords is caused, which affects the joint strength. The change of horizontal spacing of steel cords compared to vertical spacing has a more significant effect on the equivalent stress of steel cords, which is more likely to cause the failure of joint steel cords. The preformed core rubber laying technology can effectively reduce the offset of steel cords, among which the semicircular core rubber groove has the best effect, reducing by 70% in the horizontal direction and 86.9% in the vertical direction. Under the same vulcanization conditions, compared with filling core rubber, the adhesive strength after vulcanization of triangular, trapezoidal, and semicircular core rubber grooves increased by 1.91%, −3.51%, and 2.48%, respectively, with the best combination with semicircular core rubber. The preformed core rubber technology with semicircular core rubber groove laying can reduce the working time by 70% while concurrently boosting the joint strength of the vulcanized conveyor belt by 5.74%. The research findings can offer both theoretical and practical insights for streamlining joint enhancements.