The invention discloses a diesel engine variable altitude variable flow cooling system, which includes a variable altitude variable cooling liquid flow system, a variable altitude variable cooling airflow system and a control system, wherein the variable altitude variable cooling liquid flow system includes a variable flow cooling water pump, a variable temperature thermostat, and a radiator; a cooling fan of the variable altitude variable cooling air flow system is connected with a hydraulic control device; and the control system includes an ECU, a first temperature sensor, a second temperature sensor, a flow sensor, and two cooling liquid flow sensors, wherein the first temperature sensor is installed on a cooling liquid outlet pipeline between an outlet of a diesel and the variable temperature thermostat, the second temperature sensor is installed on a cooling liquid pipeline of an outlet of the radiator, the flow sensor is installed on the cooling liquid outlet pipeline between the outlet of the diesel and the variable temperature thermostat, and the two cooling liquid flow sensors are respectively installed on two outlets of the variable temperature thermostat. According to the diesel engine variable altitude variable flow cooling system, real-time optimum control of the cooling temperature of the diesel can be realized within the altitude range of 0 to 5500 m.