The Faver-averaged N - S equations and k - ? model are solved by using the finite volume method , and a numerical emulation is done for the micro-jet actuators in modifying the aerodynamic performance of a cylindrical body . The result shows that the aerodynamic performance of a cylindrical body is modified, and "low pressure recirculation region " produced is a root cause of the modification. And the calculating results are in agreement with the phenomena observed in the experiments of the documents.