The present invention relates to the field of sealing glues, particularly to a one-component caulking waterproof sealing glue for railway ballastless tracks, and a preparation method thereof, and provides a one-component caulking waterproof sealing glue, which comprises, by weight, 15-25 parts of a silane-terminated polyether, 5-15 parts of polyether triol, 5-15 parts of polyether diol, 5-20 partsof a cross-linking agent, 1-5 parts of a water removing agent, 40-60 parts of a reinforcing agent, and 0.01-0.1 part of an organotin catalyst. According to the present invention, the one-component caulking waterproof sealing glue does not contain white oil, asphalt, waste rubber and solvents, is odorless, non-toxic, environmentally friendly and ecological, is suitable for high-frequency flexing application, cannot disengage under long-term force applying deformation after bonding so as to achieve long-term sealing waterproofing property, can prevent foreign matters from being embedded, is adapted to dynamic load deformation, and is suitable for the expansion joints, the deformation joints, the construction joints, the structure joints and the settlement joints of concrete structures withlarge dynamic loads.