The invention discloses a vehicular fatigue driving monitoring system; a Doppler radar detection unit for detecting physiological signal changes of a driver is mounted in a cab and comprises a Doppler radar sensor, a power module, a signal preprocessing module, a differential amplifier, an active bandpass filter, a respiratory and heartbeat signal separation module and a MCU (microcontroller unit) module, wherein the Doppler radar sensor is used for transmitting continuous wave radar signals to a human chest and outputting low-frequency signals, the low-frequency signals are sequentially subjected to multistage signal treatment, and the MCU module acquires human a body respiratory signal and a heartbeat signal and judges whether the driver is in fatigue driving state or not according to the changes in the body respiratory signal and heartbeat signal. Compared with the prior art, it is proposed for the first time that fatigue level of a driver is monitored by means of Doppler measurement technology, detection of steering wheel angle information is added to the system, and fatigue driving measurement precision is improved through multi-source information processing.