We investigate effect of isospin dependence of nucleon-nucleon (N-N) cross sectionσNNiso on the nuclear stopping R (momentum dissipation) as the increase of neutron-proton ratio of collision system in heavy ion collisions. This effect is indicated by the difference between R’s for isospin independent in-medium N-N cross sections;σ1noiso and isospin dependent in-medium N-N cross sectionσNNiso.Where the isospin independent N-N cross sectionσ1noiso is defined asσnn=σpp=σnp. An empirical isospin dependent expression of the inmedium nucleon nucleon cross section is We investigate effect of isospin dependence of nucleon-nucleon (NN) cross section σNNiso on the nuclear stopping R (momentum dissipation) as the increase of neutron-proton ratio of collision system in heavy ion collisions. This effect is indicated by the difference between R’s for isospin independent in-medium NN cross sections; σ1noiso and isospin dependent in-medium NN cross sectionσNNiso. Where the isospin independent NN cross sectionσ1noiso is defined as σnn = σpp = σnp. An empirical isospin dependent expression of the inmedium nucleon nucleon cross section is