Abstract: The PGNAA facility at CARR was designed and optimized using Monte Carlo methods. The general configuration as well as physical and geometrical parameters for the key components of the facility has been defined. A neutron filter of 20 cm length mono-crystal Bismuth could result in a high thermal neutron flux with low epithermal neutron and gamma ray contaminations. The collimator with a ‘sandwich structure’ was selected from three candidate structures for its superior performance in obtaining high neutron flux and low background. Factors including the weight, volume, machinability, cost low bachground at the detector position were taken into account in the optimization of the radiation shielding design. The simulation results showed that the design meets the requirements of radiation protection, and low gamma background.