A measuring system provided by the invention transforms the light intensity into a current signal by using a photoelectric sensor, thereby realizing measurement of a wave frequency and a wave speed of a fluctuating liquid membrane. According to the principle of the system, when light emitted by an infrared light-emitting diode passes through a fluctuating liquid membrane interface, color dispersion is carried out and only the part of light is absorbed by an infrared photodiode. One pair of infrared light-emitting diode and infrared photodiode installed on the outer wall of a tested segment pipe form an upper stream sensor and a lower stream sensor; the sensors transform light intensity signals into current signals; after amplification by an amplifier, an A/D converter converts the amplified signals into discrete digital signals; and on the basis of FFT and a cross-correlation analysis principle, the digital signals are processed by using an MATLAB software programming program to obtain a wave frequency and a wave seed of a fluctuating liquid membrane. The system has the following beneficial effects: the wave frequency and the wave seed of the fluctuating liquid membrane are measured simultaneously; and the statistic uncertainty of measurement data is not lower than 5%.