The single-spin-flip Metropolis-Monte-Carlo algorithm is applied to the study of phase diagram of Ising ferromagnet with mixed spins of S = l/2 and S = 1 with a crystal field interaction on the honeycomb lattice. The phase diagram we obtained is very close to the exact solutions and better than the results of effective field theory with correlations. All these make us arrixe the conclusion that the Metropolis Monte Carlo algorithm can also be used to study the mixed-spin model.