The invention discloses a method of computing a seal locking structure for a pressure vessel. The method comprises the steps that firstly a formula for computing the minimum required sealing force of the seal locking structure under the pressure effect is obtained based on the principle of equilibrium; an average shear stress expression of the middle section of a shear ball is obtained; according to the relationship between the center circle diameter L of a ring-shaped channel and the radius r of the shear ball, the average shear stress expression required by the seal locking structure is obtained, and the average shear stress is calculated; the average shear stress and the allowable shear stress of the shear ball material are compared, if the average shear stress is less than the allowed shear stress, the design meets the requirements, and the number of shear steel balls is determined. The judgement criterion and the number of the shearing strength of the shear stress ball are determined by the method, a reference is provided for the design of the seal locking structure, and the relationship between the parameters is given, and an important basis is provided for the optimization design of the new seal locking structure.