The knowledge of flow regime is very important for quantifying the pressure drop,the stability and safety of two-phase flow systems.Based on image multi-feature fusion and support vector machine,a new method to identify flow regime in two-phase flow was presented.Firstly,gas-liquid two-phase flow images including bubbly flow,plug flow,slug flow,stratified flow,wavy flow,annular flow and mist flow were captured by digital high speed video systems in the horizontal tube.The image moment invariants and gray level co-occurrence matrix texture features were extracted using image processing techniques.To improve the performance of a multiple classifier system,the rough sets theory was used for reducing the inessential factors.Furthermore,the support vector machine was trained by using these eigenvectors to reduce the dimension as flow regime samples,and the flow regime intelligent identification was realized.The test results showed that image features which were reduced with the rough sets theory could excellently reflect the difference between seven typical flow regimes,and successful training the support vector machine could quickly and accurately identify seven typical flow regimes of gas-iquid two-phase flow in the horizontal tube.Image multi-feature fusion method provided a new way to identify the gas-liquid two-phase flow,and achieved higher identification ability than that of single characteristic.The overall identification accuracy was 100%,and an estimate of the image processing time was 8 ms for online flow regime identification. The knowledge of flow regime is very important for quantifying the pressure drop, the stability and safety of two-phase flow systems. Based on image multi-feature fusion and support vector machine, a new method to identify flow regime in two-phase flow was presented.Firstly, gas-liquid two-phase flow images including bubbly flow, plug flow, slug flow, stratified flow, wavy flow, annular flow and mist flow were captured by digital high speed video systems in the horizontal tube. The image moment invariants and gray level co-occurrence matrix texture features were extracted using image processing techniques. To improve the performance of a multiple classifier system, the rough sets theory was used for reducing the inessential factors. Futurertherm, the support vector machine was trained by using these eigenvectors to reduce the dimension as flow regime samples, and the flow regime intelligent identification was realized. the test results showed that image features which were reduced with the rough sets t heory could excellently reflect the difference between seven typical flow regimes, and successful training the support vector machine could quickly and accurately identify seven typical flow regimes of gas-iquid two-phase flow in the horizontal tube. Image multi-feature fusion method provided a new way to identify the gas-liquid two-phase flow, and achieved higher identification ability than that of single characteristic. The overall identification accuracy was 100%, and an estimate of the image processing time was 8 ms for online flow regime identification.