Two main results will be presented in our paper. First, we will prove the regularity of solutions to axially symmetric Navier-Stokes equations under a log supercritical assumption on the horizontally radial component u r and vertical component u z , accompanied by a log subcritical assumption on the horizontally angular component u θ of the velocity. Second, the precise Green function for the operator −(∆ − 1 r 2 ) under the axially symmetric situation, where r is the distance to the symmetric axis, and some weighted L p estimates of it will be given. This will serve as a tool for the study of axially symmetric Navier-Stokes equations. As an application, we will prove the regularity of solutions to axially symmetric Navier-Stokes equations under a critical (or a subcritical) assumption on the angular component w θ of the vorticity.