The invention provides a control device and a method thereof for a locomotive charger. In order to solve the problem that the existing locomotive charger has no temperature compensation function, and aiming at the charging control discontinuity of the charger, the invention is provided. The control device comprises a judgment unit, a voltage collection unit, a current collection unit, a floating charge control unit, a rapid charge control unit, a temperature collection unit, a voltage compensation unit and an execution unit, wherein the judgment unit is respectively connected with the voltage collection unit, the current collection unit, the floating charge control unit, the rapid charge control unit, the temperature collection unit, the voltage compensation unit and the execution unit. The invention has the advantages that the charge process can be controlled according to the temperature and the real-time voltage and current of an accumulator, and the charging is safer and more stable.