By using the Isospin Dependent Quantum Molecular Dynamics Model (IQMD), we show the influence of initial N/Z, isospin symmetry potential and medium correction of two-body cross sections on equilibration in momentum space in intermediate energy heavy ion collisions. By investigating the isospin distribution in emitted nucleons, light charged particles and intermediate mass fragmentations for four mass symmetric and isospin asymmetric96+96systemsRu+Ru,Ru+Zr,Zr+Ru,andZr+Zrat 400 AMeV and 100 AMeV we further study the degree of equilibration with respect to isospin degree of freedom in intermediate energy heavy ion collisions. We also propose the sensitive probes to the degree of equilibration in intermediate energy heavy ion collisions. ©2001 American Institute of Physics.