Abstract: Supercharging technology can increase the power density of free-piston engine generators. In this paper, a one-dimensional simulation model was developed for a free-piston engine generator and calibrated based on experimental data. The effects of parameters such as intake and exhaust pressures, port timing and intake and exhaust pipe geometry on its performance were investigated based on the boost mode simulation. And then the electric boosting scheme was designed, the matching parameters were determined, and an electric air compressor was selected. The results show that when the intake pressure exceeds 0.18 Mpa, the brake power can exceed 10 kW. The scavenge ratio needs to be maintained at about 1.3, and the scavenge efficiency can reach up to 90%. To ensure sufficient intake volume and good air exchange quality, the scavenging port needs to be opened over 0.74 ms in advance and the intake pipe volume needs to be expanded appropriately. The matching results show that the flow characteristic line of the free-piston engine generator can cross the compressor high efficiency zone at the rated operating frequency and that the compressor efficiency can exceed 73% under the design point operating condition.