In this paper, the coupling equations for electric field, carrier density, optical-field and temperature are simulated self-consistently in double oxide confined vertical cavity surface emitting laser therefore the characteristics threshold are studied. The potentials near the oxide layers and the activity region are obtained and the effect of current aperture edge is simulated. The distributions of threshold injected current density, carrier density, fundamental mode and temperature for different radii of double oxide confined current aperture are obtained. An appropriately confined radius of current aperture for minimum threshold injected current is found, and the structure of vertical cavity surface emitting laser is designed.