Abstract: The cross correlator is the core device of measurement system of correlation two-phase-flow.The paper introduced working principle and cross correlation algorithm of measurement system of correlation flows and design of a cross correlator based on NIOSⅡ embedded soft-core processor.It also expounded general structure,design of hardware and software of the cross correlator.The experiment of Matlab simulation verified the cross correlator can achieve cross-correlation operations of random noise signals.The cross correlator has features of good real-time,simple hardware structure and high reliability comparing with the traditional cross correlator,and can meet with the demand of online measurement for correlation flows.