A new monitoring system of the flow states of gas-liquid two-phase flow has been developed by using a differential pressure transducer combined with wavelet analysis and fuzzy pattern recognition technique. The differential pressure signal of gas-liquid two-phase flow was obtained under the states of the different flow patterns. including bubble flow. flow, slug flow, plug flow and annular flow. The acquired differential pressure signals were analyzed by the wavelet transform and the eigenvalues were extracted. The flow state of the system was mnitored by fuzzy pattern recognition technique. The experimental results show that the developed system can moinitor flow states of horizontal gas-liquid two-phase folw effectively.