Compared with the experimental data, the Fluent commercial software was used to study the mixing of the external round jet flow field in this paper. Under the same conditions with duty ratio A 10% and mass flow rate ratio Cm 0.05% for the primary jet and microjet, the micro excitation frequency of the jet and main jet vortex frequency ratio FV/FO was varied from 0 to 2, and the mixing of the flow field mixing effect of the lateral and vertical distribution of pulse were obtained. The results show that the flow field of the flow state is sensitive to the change of pulse excitation frequency; The entrainment mixing enhancement is obvious, and the structure of flow vortex is not only more rule, but also in the process of spreading outward development to entrain more fluid mixing when the micro jet excitation frequency FV is equal to the large eddy frequency FO.