In order to study the horizontal particle separator, equipped in the External-Fired Gas Turbine system (EFGT), the model experimental investigation and numerical simulation have been set up. The particle separator is used for separate small particles from gas by passing the flow through a spiral, which creates a centrifugal force. The particles will be trapped to a collector before reaching the gas exist. This study aims to analyze the efficiency of separation based on various designs of screw and cone. The experimental results show that decreasing of the cone length, the system pressure loss could be significantly reduced and the capacity of particles capture could be increased. However, the deepest cone position provides the higher loss comparing to the others. Moreover, it is evidently that the reducing number of screw’s turn and it s pitch, the better capture capacity of the separator could be obtained. In parallel, the numerical simulation has been setup to support the experimental studies. The conditional parameters, including number of mesh, air mass flow rate and outlet condition, have been varied. In addition, the validation of flow simulation has been accomplished. The results show that there is the compatibility between the numerical simulation and experimental investigation as well.