The invention relates to a method and a device for detecting the acidity of boxed dairy products. The device comprises a capacitance collection and output module for collecting a capacitance value of a detected milk sample, converting the capacitance value into a voltage value and outputting the voltage value; a pressure collection and output module for collecting and outputting static and/or dynamic pressure distribution information of a contact face of the milk sample and the pressure collection and output module; and a data process and output module which is connected with the capacitance collection and output module and the pressure collection and output module respectively and is used for receiving and operating the voltage value and the pressure distribution information output by the capacitance collection and output module and the pressure collection and output module so as to obtain and output a PH value of the detected milk sample. According to the invention, a capacitance-based non-destructive detecting device and a method thereof are disclosed; detection of the dairy products can be processed quickly and conveniently, and thus theanalysis time is saved and waste of the dairy products is avoided.