The invention discloses a compression ignition engine used for a monorail agricultural transport vehicle. The compression ignition engine comprises a base, a protective casing, a motor and a vent valve, wherein an air cylinder is mounted above the base; an igniter is arranged above the air cylinder and positioned between the air cylinder and the protective casing; a distributing valve is arranged above the protective casing; a spark plug is arranged above the distributing valve; a fixing bolt is mounted below the spark plug and arranged above the motor; a pressurization piston is arranged below the motor; a heat dissipation hole is formed in a part below the pressurization piston; a flywheel is mounted above the vent valve; a pressure rod is arranged above the flywheel. The compression ignition engine used for the monorail agricultural transport vehicle has the benefits as follows: compression ignition is effectively carried out, an effective support is provided for the kinetic energy of an internal combustion engine, the heat value is improved, exhaust gas is effectively treated, equipment openings and channels are prevented from being blocked, the service life is prolonged, and the safety and reliability in the agricultural transportation process is improved.