In order to understand the ignition properties of plasma jet, a simulation experiment has been conducted, to explore the characterization of plasma jet propagation in air under different discharge energy. Based on the experiment, a two-dimensional-axisymmetric mathematical model was developed, and the Fluent software was used to simulate the unsteady plasma jet propagation in air. The influence of discharge energy on plasma jet propagation in air was studied by changing total pressure of plasma nozzle. The results indicate that: the pressure, temperature and velocity in the plasma jet flow field are of strong vibration, temporally. As the axial displacement far away from the nozzle, the influence of discharge energy on pressure, temperature and velocity of plasma jet become less. The change of discharge energy has some effect on the surface wave and entrainment phenomena which happened when the plasma jet into air.