The evolution of micro synthetic jet in a still ambient has been studied numerically. Unsteady computations of incompressible laminar flow have been performed for an axisymmetric numerical formulation for an orifice diameter of 50 micrometers. The diaphragm was assumed to oscillate sinusoidally in time and parabolically in space. Vortex pair trajectories were visualized by extracting the vortex cores from the flow data. It was demonstrated that centreline jet velocity reveals the propagation of vortex rings and dynamics of its peak value corresponds to the movement of the vortex cores. Furthermore, it was shown that the location of maximum vorticity could not be used to identify the location of the core.