The invention provides a mass and flow measuring method and a device of a refrigerant in a refrigerating system and a measuring instrument. The method comprises the steps of: obtaining an intake temperature of a first compressor, an exhaust temperature of a second compressor, an evaporation pressure, a condensation pressure, shell surface temperatures of the first and second compressors, a surrounding environment temperature, a total consumption power, a spraying temperature, a first supercooling temperature, a second supercooling temperature and an oil content of a refrigerant mixture; calculating corresponding first, second, third, fourth and fifth enthalpy values, enthalpy value differences and total heat exchange quantities of the first and second compressors with external environment according to the obtained data; and calculating the mass and the flow of the refrigerant in the refrigerating system according to the first, second, third, fourth and fifth enthalpy values, the enthalpy value differences, the total consumption power, the total heat exchange quantities and the oil content of the refrigerant mixture. The method realizes non-invasion and high-precision measurement of the mass and the flow of the refrigerant in the refrigerating system, prevents adverse effect on the refrigerating system in the measuring process, and improves the user experience.