Scattering of incident light by the interstellar dust is usually approximated by Henyey-Greenstein scattering phase function. Recently, Draine (2003) proposed a new analytic phase function with two parameters. We describe an algorithm to generate random numbers distributed according to the Draine’s function, and compare two phase functions. It is also derived exact solutions of two parameters for given values ${langle}cos{ heta}{ angle}$ and ${langle}cos^2{ heta}{ angle}$. It is found that Henyey-Greenstein function with g = ${langle}cos{ heta}{ angle}$ provides a good approximation for ${lambda};>;2000{AA}$. At shorter wavelengths, more realistic phase function may be needed for radiative transfer models.