Stable heat field distribution in dielectric apertured vertical-cavity surface-emitting laser(VCSEL) was analyzed by using numerical calculation.The results show that the variation of heat field distribution is mostly affected by the thermal conductive ability of DBR region and the difference of thermal conductive ability of DBR region and dielectric confinement layer,the highest temperature center is near dielectric aperture of VCSEL,and the temperature distribution along active layer appears evidence temperature step (plateau just below the dielectric aperature) which helps to form the refractive index step in active layer.