We propose a method for the evaluation of the flow rate of cryogenic two-phase flows in flowmeters without separation based on the Venturi tube. The proposed procedure takes into account the equations of state of two-phase medium, i.e., the changes in density, mass vapor quality, and temperature of cryogenic twophase flows depending on the level of pressure in the Venturi tube. It is shown that if we do not take into account the evolution of the parameters of flow, then we get an additional error in the evaluation of the flow rate. Hence, it is impossible to correctly determine the sensitivity and measurement range of the flowmeter. We determine the optimal range of measurements of the pressure drop and propose a procedure of measurement of the flow rate of two-phase cryogenic flows according to the temperature drop in the Venturi tube. The problem of measurement of the flow rates of two-phase cryogenic flows is urgent for accelerators, as well as for the aerospace and gas-transportation equipment.