A drink driving online control system based on photoelectric detection technology is introduced in the paper. The system can take the initiative to force motor vehicle drivers to test their drinking status, and reasonably control the driver’s behavior accordingly. The basic principle is to use the characteristic that 1185nm wavelength IR is absorbed by alcohol the most easily to detect the motor vehicle driver’s alcohol concentration and to determine the extent of motor vehicle drivers drinking. The alcohol concentration detected is converted into photoelectric signal that is handled by 89C2051 MCU. The signal handled is exported to voice devices to get voice prompts and warning, and exported to the relay of ignition circuit system to cut off the ignition system to control the engine’s starting and prevent the driver drunk driving, and exported to electro-hydraulic proportional flow valve to control the maximum speed of motor vehicle according to the driver’s alcohol content. The purpose of this study is to be able to effectively solve the problem of drink driving and avoid serious traffic accidents resulting from drunken driving.