The reflection effect of the spherical surface of a hemisphere solid immersion lens (SIL) has been investigated using the vectorial diffraction theory for high numerical aperture systems. The results showed that this reflection had an important influence on the transmitted field intensity of the SIL microscopy system. However,the reflection on the spherical surface of a hemisphere SIL did not change the resolution of the hemisphere SIL microscopy system. The larger mismatch in refractive indiced on both sides of the SIL's spherical interface results in the less transmission intensity of the system. This disadvantage could be overcome by using one layer of antireflecting film that was coated on the SIL's spherical surface or by filling the space between the objective and the SIL with a material with large (but smaller than SIL's) refractive index.