The non-equally-probable step-function (NEPSF) representation has been proposed as a new method for selecting scattering angles from a multigroup transfer matrix for a medium of a single nuclide or a mixture. This technique avoids the disadvantage of the equally-probable step-function representation, which cannot well present the group-to-group transfer lax for a mixture. Similar to the discrete angle representation, the NEPSF representation can preserve precisely the moments of the scattering law; moreover, it has the advantage of eliminating ray effects. We give semianalytical procedures for obtaining P3 and P5 NEPSF representations, which will facilitate greatly low-order transfer matrix treatment in multigroup Monte Carlo.