The interaction effects of other geometric parameters on the optimized value of a certain geometric parameters of spiral groove dry gas seal (DGS) in low pressure are analyzed for the purpose of solving the problem of the interaction effect of geometric parameters of hydrodynamic groove on objective function that have been ignored in optimization design of hydrodynamic groove of DGS which leads to the inaccuracy of optimized value of geometric parameters. Geometrical and mathematical model of spiral groove DGS are set up according to the theory of gas lubrication. The pressure distribution and steady performance are obtained by solving the Reynolds equations by using finite difference method

and several characterized parameters of spiral groove are defined. The change rules of optimized values for the maximum film stiffness of a certain geometric parameter of spiral groove with other geometric parameters in different operation velocity are presented. The results show that complicated interaction effect relationship existed between the geometric parameters of spiral groove DGS

of which suit for the three comprehensive design criteria

including decrease the amplitude changes of real flow area of groove

groove length-width ratio and groove length-depth ratio. The maximum film stiffness obtained by the optimization method of considering the interaction effect of geometric parameters is about 11.4% which is larger than that obtained by the single factor optimization method in the given example.