A constant contact steel spring crack preventing method and a vertical backstop are provided. A revolving body-shaped rubber boss is arranged over a rubber main body; the rubber boss has a contact with a framework guide cylinder upon zero load of a locomotive; rigidity of the vertical backstop can be adjusted via adjustments of the diameter or the height of the rubber boss and the rubber main body; an included angle between an annular straight flat section of the rubber main body and a horizontal surface is adjusted, so variable rigidity of the vertical backstop can be adjusted; the rubber boss is connected with the rubber main body via an annular arc-shaped section; times of variable rigidity of the vertical backstop can be adjusted via adjustments of section numbers of the annular arc-shaped section of the vertical backstop; a pedestal is embedded into the rubber main body of the vertical backstop, so the pedestal can space the vertical backstop; positions of a vertical backstop spacing position and rigidity of the vertical backstop can be adjusted via adjustments of the height of the pedestal; vertical load of a steel spring can be reduced via adjustments of rigidity, variable rigidity and spacing position of the vertical backstop; and metal fatigue of the steel spring during the operation of the locomotive can be reduced, so steel spring crack can be prevented therefore.