The invention relates to a car blind spot monitoring and early-warning system. The car blind spot monitoring and early-warning system comprises an out-car device, an in-car device, and a rearview mirror adjustment device, wherein the out-car device comprises an out-car controller, a detection radar and an out-car alarm device, the detection radar detects obstacles entering the blind spot of an car, and sends a monitoring signal to the out-car controller, and the out-car controller alarms outside a car through the out-car alarm device; the in-car device comprises an in-car controller and an in-car early-warning device, the input end of the in-car controller is electrically connected with the out-car controller, the output end of the in-car controller is electrically connected with the in-car early-warning device and the rearview mirror adjustment device to receive the monitoring signal and conducts early warning on drivers through the in-car early-warning device according to the monitoring signal, and adjusts the angle of a rearview mirror by calculating and controlling the rearview mirror adjustment device; and the rearview mirror adjustment device comprises the rearview mirror anda steering gear mechanism for driving rotation of the rearview mirror, and the control signal input end of the steering gear mechanism is electrically connected with the output end of the in-car controller. According to the car blind spot monitoring and early-warning system and method, the hidden safety hazards caused by the car blind spot are reduced advantageously, and the traffic safety is improved.