The invention discloses a train and an onboard control system thereof. The system comprises an onboard controller, the onboard controller comprises a logic operation unit, a first IO interface unit and a second IO interface unit, the logic operation unit and the first IO interface unit are both disposed at one end of the train, the second IO interface unit is disposed at the other end of the train, and the logic operation unit is connected with the first IO interface unit and the second IO interface unit through an industrial field bus respectively; the logic operation unit is used for controlling the train to execute controlling commands corresponding to control signals according to the control signals at least including key activation signals of the train collected by the first IO interface unit or the second IO interface unit, and the logic operation unit is used for determining the running direction of the train based on the key activation signals. The system can achieve a bidirectional automatic driving function, reduces a set of logic operation units in configuration, and has low cost and high competitiveness.