The utility model provides a novel rail lower bolster, this rail lower bolster (1) includes backing plate (2), its characterized in that, backing plate (2) are foam structure, and wherein, backing plate (2) both sides set up flange (3) along the sleeper direction. Through the utility model provides a rail lower bolster can be fine the too big problem of solution flat structure rigidity. Simultaneously, flat structure is not owing to exist the slot, and also the backing plate edge turns up with regard to not existing, there is the stress concentration point in base plate structure, produce theproblem of tearing the phenomenon.