Abstract: The status of online identification for gas-liquidtwo-phase flow regime using the parameter fluctuation isreviewed. This paper mainly discusses the mechanism for thetwo-phase flow parameter fluctuation, the application ofwavelet theory, feature extraction and analysis of thefluctuation, and realizing methods. In particular, itemphasizes both the statistical and nonlinear analysis andtheir relationship with flow regimes. Furthermore, the neuralnetwork method to identify flow regimes and its developmentare reviewed and discussed in detail. The research advance isdiscussed in the selection of fluctuating parameters, thephysical interpretation of the fluctuations and the identificationmethod.