Abstract: A compressible round jet is investigated by large eddy simulation.The jet Mach number is 0.75 and the Reynolds number is 50 000.Numerical results are validated by available experimental data.Two major stages for the shear layer instability development are observed and analyzed.After this,two-point space-time correlations of axial velocity fluctuation u',radial velocity fluctuation v' and pressure fluctuation p' in the shear layer are investigated.Their distribution and evolution in time and space are presented and discussed.The migration characteristics of vortices are analyzed.The study provides a base for further investigation and controlling of jet noise.