The invention belongs to the relevant technical field of dual-fuel automobiles, and discloses a vehicle-mounted methanol cracking reactor control system. The vehicle-mounted methanol cracking reactor control system comprises a methanol cracking reactor, a temperature sensor, a methanol spray nozzle, a methanol pump, a methanol box and an auxiliary controller, wherein the methanol cracking reactor communicates with the methanol spray nozzle; the temperature sensor is arranged on the methanol cracking reactor; the methanol spray nozzle is connected with the methanol pump through an oil supply pipe; the methanol pump is arranged in the methanol box. The auxiliary controller realizes communication with a primary controller through a CAN (controller area network) bus, so that the operation parameters of an engine are obtained from the primary controller in real time; the auxiliary controller is also used for collecting temperature data detected by the temperature sensor; the auxiliary controller controls the methanol pump and the methanol spray nozzle to regulate the methanol supply quantity according to the engine parameters, the temperature data and a methanol supply quantity MAP obtained through experiments.