A constant contact method for preventing steel spring break in a suspension system for a railway locomotive comprising the steel spring and a vertical backstop, wherein: -- the steel spring is arranged between the bogie frame and an axle box, -- the vertical backstop is located in the steel spring, -- a frame tank is located on the bogie frame right above the vertical backstop, characterized in that the vertical backstop comprises a rubber main body, a rubber convex platform and a pedestal, wherein a revolve solid shaped rubber convex platform is provided above the rubber main body, the rubber main body is provided with an annular straight section and an annular arc section, the rubber convex platform is connected with the rubber main body via the annular arc section, a pedestal is provided underneath the rubber main body, and the bottom of the rubber main body is provided with a cavity, wherein the rubber main body, the rubber convex platform and the pedestal are an entirety, wherein, -- the pedestal is made of metal, -- the rubber convex platform comprises the top of the convex platform and the outside of the convex platform and the rubber convex platform has the form of a truncated cone, -- the rubber main body is provided with at least 3 annular straight sections (111, 112, 113) and each annular straight section and the horizontal plane has angle in between, -- when the locomotive is non-loaded, the rubber convex platform touches the frame tank; -- by adjusting the diameter or the height of the rubber convex platform, the rigidity of the vertical backstop can be adjusted, and by adjusting the diameter or the height of the rubber main body, the rigidity of the vertical backstop can also be adjusted; -- the variable rigidity of the vertical backstop can be adjusted by adjusting the angle between the annular straight section and the annular arc section; -- by adjusting the number of segments of the annular arc section of the vertical backstop, the number of the variable rigidity of the vertical backstop can be adjusted; -- the pedestal is embedded in the rubber main body of the vertical backstop, so that the pedestal can limit the vertical backstop, and by adjusting the height of the pedestal, the rigidity as well as the positions limited by the vertical backstop can be adjusted; -- by adjusting the rigidity, variable rigidity as well as the position limited of the vertical backstop, the vertical load born by the steel spring is reduced, the metal fatigue produced by the steel spring during the locomotive running is reduced, so that the break of the steel spring is avoided. -- the steel spring is arranged between the bogie frame and an axle box, -- the vertical backstop is located in the steel spring, -- a frame tank is located on the bogie frame right above the vertical backstop, -- the pedestal is made of metal, -- the rubber convex platform comprises the top of the convex platform and the outside of the convex platform and the rubber convex platform has the form of a truncated cone, -- the rubber main body is provided with at least 3 annular straight sections (111, 112, 113) and each annular straight section and the horizontal plane has angle in between, -- when the locomotive is non-loaded, the rubber convex platform touches the frame tank; -- by adjusting the diameter or the height of the rubber convex platform, the rigidity of the vertical backstop can be adjusted, and by adjusting the diameter or the height of the rubber main body, the rigidity of the vertical backstop can also be adjusted; -- the variable rigidity of the vertical backstop can be adjusted by adjusting the angle between the annular straight section and the annular arc section; -- by adjusting the number of segments of the annular arc section of the vertical backstop, the number of the variable rigidity of the vertical backstop can be adjusted; -- the pedestal is embedded in the rubber main body of the vertical backstop, so that the pedestal can limit the vertical backstop, and by adjusting the height of the pedestal, the rigidity as well as the positions limited by the vertical backstop can be adjusted; -- by adjusting the rigidity, variable rigidity as well as the position limited of the vertical backstop, the vertical load born by the steel spring is reduced, the metal fatigue produced by the steel spring during the locomotive running is reduced, so that the break of the steel spring is avoided.