Vector discrete-ordinate radiative transfer method (VDISORT) was orignianally developed by Weng (1992) and improved by Weng and Liu (2003). This model can be used to calculate intensity, polarization, and polarimetric radiance and radiance gradient within ultraviolet, visible, infrared, and microwave ranges. The solution within any layer is given by the optical properties and Planck source function of the layer. The coefficients in the general solutions are derived through a linear algebra system where the continuality at top and surface boundaries as well as at adjoint boundaries of layers is applied. VDISORT derives radiances as analytic form and can serve as a reference to validate other radiative transfer models in planetary atmosphere. Its analytical formulas for radiance and radiance gradient also allow some direct sensitivity studies