The invention relates to an automatic liquid concentration detection method and device. The device is simple in structure, simple to maintain, high in adaptability, low in working environment requirement, high in precision and accuracy and applicable to automatic detection of concentration of various solutions. The device comprises a single-chip microcomputer, a camera, a buoyance gauge, a temperature sensor, a solenoid valve, a sampling pump, measuring software and an LCD (liquid crystal display), wherein the single-chip microcomputer is connected with the camera, the temperature sensor, the LCD and the solenoid valve; the camera is connected with the single-chip microcomputer and used for acquiring an image signal of the buoyance gauge; the temperature sensor is connected with an input end of the single-chip microcomputer and used for detecting the temperature of a liquid in real time; the solenoid valve is connected with the single-chip microcomputer and used for switching the to-be-detected liquid or clear water for washing; the sampling pump is connected with the single-chip microcomputer and used for pumping the liquid into a sample tank. The single-chip microcomputer and the camera acquire an image of the buoyance gauge, concentration information of the liquid is acquired through calculation of the position of the buoyance gauge in the image, meanwhile, the temperature of the liquid is acquired, temperature correction is performed on the concentration, and the result is displayed by the LCD. Automatic measurement and online detection are realized.