The invention relates to a method for characterizing the mixture concentration field of liquids, in particular to a method for characterizing the concentration field of the entire mixture region by using the characteristics of decoloration color changes after different liquids are mixed. A colorless NaS2O3 solution is used as a flow-entraining agent A of water, a blue starch I2 solution is used as a flow-entraining agent B of pesticide, the water with the flow-entraining agent A and the pesticide with the flow-entraining agent B are simultaneously injected into a mixer for mixing, and along with the mixing process, the color of mixed liquids can change. A part of the mixed region of the mixer adopts a translucent material, through the translucent mixed region, a high-speed CCD (Charge-Coupled Device) camera captures pictures after the water is mixed with the pesticide, and concentration field information is characterized after processing the captured pictures with image processing technologies, such as grey scale binary, level set, boundary tracking and the like. The invention has the advantages of simplicity, practicality, low cost and good maneuverability.