In this chapter, a summary of numerical algorithms solving the radiative transfer equation (RTE) is presented. These algorithms could be roughly classified into two categories. The one is ray-tracing methods, including the Zone method, Monte Carlo method, and discrete transfer method. The stochastic approach of Monte Carlo codes is widely used, since its flexible applicability to arbitrary multidimensional configurations. The others are methods based on the discretization of the differential form of RTE, including the spherical harmonics method, discrete ordinates method, and finite volume method.