A stochastic approach based on two-dimensional dynamical model has been used to simulate the fission dynamics of the excited compound nucleus 251Es produced in 19F 232Th reaction. In the dynamical calculations the elongation parameter has been used as the first dimension and the projection of the total spin of the compound nucleus onto the symmetry axis,K , considered as the second dimension. The value of post-saddle friction was inferred by reproducing experimental data on the mean pre-scission neutron multiplicity for 251Es . It was shown that the results of calculations are in good agreement with the experimental data by applying values of the post-saddle friction equal to 13-15 *10^21 s^-1