The invention discloses a simplified multi-mode vehicle detector which comprises a microprocessor, a geomagnetic sensor chip, an operational amplifier, a radar ranging module, a power supply unit, a microwave radio frequency communicator, a matched transceiving antenna of the microwave radio frequency communicator and a visible light auxiliary detection circuit. An output signal of the geomagneticsensor chip is amplified by the operational amplifier and then is input to a geomagnetic signal input end of the microprocessor; the microprocessor is connected with the radar ranging module througha ranging interface end, is connected with the microwave radio frequency communicator through a communication end, is connected with the power supply unit through a control output end to ensure power-saving work of related parts, and is connected with the visible light auxiliary detection circuit through a light detection interface end. According to the invention, a unique grading progressive strategy is adopted to detect vehicles; in most cases, calculation is carried out by geomagnetic and / or visible light data acquired by ultra-low power consumption; the detection result with high confidence can be output without additionally starting a radar ranging module with high power consumption, the detection accuracy is considered, the product battery replacement and scrapping speed is greatly reduced, the product is flexible, economical and practical, a large amount of manpower and material resource operation and maintenance investment can be saved, and the method is suitable for various intelligent traffic applications.