  In this work, we propose a novel method for calculating the occupation
probability in the Pauli blocking of the quantum molecular dynamics type
models. This method refines the description of the Pauli blocking ratio in the
nuclear matter and that in the finite nucleus. The influence of the new Pauli
blocking method on the heavy ion collisions observables, such as the charge
distribution, the free neutron to proton yield ratios, and the extracted
physical quantities, such as the in-medium nucleon-nucleon cross sections, are
investigated. For the extracted in-medium nucleon-nucleon cross sections, our
results show that it will be enhanced 1.1$-$2.5 times than that with the
conventional Pauli blocking method at the beam energy less than 150 MeV/u,
which highlights the importance of a refined Pauli blocking method for
developing an advanced transport model to describe complex heavy ion
collisions.
