[en] A method to research Shannon entropy characteristics of two-phase flow regimes is introduced. Shannon entropy can be calculated from power spectral density of output signal (such as pressure drop). In a test facility of two-phase flow loop, experiment was made to investigate two-phase flow regimes in vertical pipes. The experimental data of different flow regime tests were obtained by adjusting the air and water volume flow. From analyzing the Shannon entropy of different flow regimes, the authors find that the negative Shannon entropy (negentropy) of bubble flow is the smallest, slug flow's is the largest and the negentropy of annular flow is between that of bubble flow and annular flow