Abstract: In the report, the neutron flux density determination by 4πβ-γcoincidencemethod is described. In the method, the level of thermal neutron flux at theirradiation site of the PARR-II reactor is obtained by the measurement of thereactivity of gold foils irradiated there. The total fission rate is obtained byintegration method. The thermal neutron flux density per kilo-watt of power is thencalculated. A standard point is set up, and the power of the PARR-II reactorcan thus be determined.