The invention belongs to the technical field of tire rubber, and particularly relates to a formula, a mixing process and an extrusion process of a semi-steel radial tire cap strip rubber material which is suitable for an extrusion method, low in heat generation and moderate in adhesiveness. The rubber material formula comprises standard particulate rubber, trans-polycyclooctene rubber, styrene butadiene rubber, low-structure high-wear-resistance carbon black, zinc oxide, stearic acid, an anti-aging agent 4020, a resorcinol or resorcinol formaldehyde adhesive, a methylene donor adhesive, a plasticizer A, a peptizer, insoluble sulfur with high thermal stability, an anti-scorching agent CTP and a sulfonamide accelerator. The cap strip rubber material prepared by the preparation process provided by the invention has the characteristics of low heat generation, moderate bonding performance with nylon cords, suitability for production of nylon cap strips by an extrusion method and the like, is few in use personnel and high in production efficiency, is directly used during molding, is easy to unwind in a rolling manner, is not easy to adhere, and is suitable for large-scale production. Thedefects that in the using process of the nylon cap strip cord fabric roll produced through a calendering method, the viscosity between layers is large, and separation is not easy can be effectively overcome.