This paper introduced the application of pattern recognition in the measuring phase fraction of gas-powder mixed flow. Flow-through measurement system based on virtual instrument techniques; include the techniques of electrical capacitance tomography and cross-correlation velocity measurement technology. The module structure of the system is present. According the principle of the phase fraction based on pattern recognition technology, the arithmetic with C++ program is described in the paper. The experiment process for this flow-through measurement system and experiment results are described in this article.