Abstract: The structural relationship and working condition applicability of typical derived structures of spiral groove dry gas seal (DGS) were investigated under two conditions, i.e. high-speed and low-pressure, high-pressure and low-speed. The mathematical model of typical groove-land combined spiral groove DGS was established based on gas lubrication theory, and then the film pressure distribution was obtained by solving steady Reynolds equation utilizing finite difference method. Based on full factorial design method, the steady performances of typical groove-land combined spiral groove DGSs were computed numerically at different values of groove area ratio, comparison studies between typical groove-land combined spiral groove DGSs and common spiral groove DGS were conducted, and further strategy to enhance film stiffness of spiral groove DGS by structural modification was proposed. The results show that film stiffness of spiral groove DGS could be improved remarkably via the proper combinational design between basis spiral groove and additional land, thereinto film stiffness of the multi-path spiral groove DGS, where the additional land locates at the middle and upstream of basis spiral groove, was 20% larger than that of spiral groove DGS at high-speed and low-pressure. Moreover, the maximum opening force and film stiffness of groove-land combined spiral groove DGS could be obtained at different optimal values of groove area ratio.