The invention discloses a manufacturing method of an internal jacket. The method comprises the following steps: the wire rod blanks are taken as the raw materials, firstly, the spheroidizing annealing is performed to the wire rod blanks of the internal jacket, the phosphating and the fine-drawing and sizing are performed to the blanks after spheroidizing annealing, and then the multi-station cold heading automatic one-time molding and the secondary fine finishing working procedures are carried out, i.e., groove broaching, tapping, piece cutting and finally, packaging and shipment. The invention adopts the wire rod materials to replace straight rods and fracturing materials, can meet the requirement of multi-station cold heading continuous production, reduces the loss of remnants, reduces the large-area of lathe remainder of the exterior conical surface, the inner hole and the end surface after adopting the multi-station cold heading one-time molding and further reduces the loss of the raw material by 30 percent, therefore, the cost is reduced; due to the adoption of the multi-station cold heading continuous molding production, the production speed can reach 60 PCS/minute, the daily output is up to 21,000 PCS in average, the production efficiency is promoted by 7-8 times than before, and the cost of investment of manpower and material resources is greatly reduced.