Abstract: URJ 92-6 metallic tank is the oil tank carried by a road tank car.Both the theory and method of optimized design and the theory of car travelling are applied for the first time in the design of metallic tanks.Based on given mathemetic model, optimi/ation operation are conducted by optimizing hybrid discrete variables, and it is concluded that the optimal section of the tank body is ladder-shaped circle.An overall result of an URJ 92-6 tank with the largest capacity and lowest barycenter is achieved.By integrating it into objective function with weighed factor, optimal dimension combination and optimized shell thickness are obtained with the prerequisite of meeting the strength and rigidity requirements for tank body and head.In addition, URJ 92-6 metallic tank, which is suitable for stable car travelling and can ensure safe transportation, provides a sound theoretical basis and design method for optimization design of metallic tanks.