Abstract: In this paper a particle-in-cell model is used to simulate the SEE (stimulated electromagnetic emission) produced by the parametric decay instability when a powerful high-frequency electromagnetic pump O-wave is launched into F-region of the ionosphere. The simulation results show the ratio of the pump wave frequency (w₀) to the electron cyclotron harmonic frequency (w_ce) strongly influences the SEE when pump wave frequency is very close to the electron cyclotron frequency. Moreover the angle between the incident pump wave electric field and the geomagnetic field is also a considerable factor to the SEE. For example, for w₀=4.2w_ce, the SEE is obvious, when the pump electric field is perpendicular to the geomagnetic field, but if the pump electric field is parallel to the geomagnetic field, there is no SEE phenomenon.