Abstract: In this paper, the nuclear track thermal analysis method neutron detector was put forward for measuring high neutron flux density. This method was successfully validated on Miniature Neutron Source Reactor for low neutron flux density measurement. Experiments in the irradiation channels of China Advanced Research Reactor were carried out in order to fully validate the measurement of high neutron flux density. The experimental results of relative neutron flux density distributions agree with the theoretical results by MCNP very well, which means this method is suitable for high neutron flux density measurements.