System stiffness (longitudinal, lateral, and torsional stiffness) is a meaningful index for strut nose landing gear design. It arises from profound significance to explore the influence law of system stiffness on shimmy stability for the anti-shimmy design of landing gear. By changing the initial gas pressure of the buffer, the influence of buffer stroke on the system stiffness is analyzed, and the influence of the system stiffness on the initial torsion angle, convergence time, convergence ratio, and stability area of the strut nose landing gear shimmy is studied. Results show that increasing the stiffness of the strut-type nose gear system can improve the anti-shimmy performance, but increase the initial torsional angle and shimmy convergence time, and reduce the ability of the landing gear to resist external disturbances. Therefore, the stiffness of the strut-type nose landing gear system cannot be excessively increased, which provides a guiding significance for its anti-shimmy design.