The research shows the experimental results for a free piston linear engine according to operation conditions of the linear engine and the structure of linear generator for generating electric power. The powerpack used in this paper consists of the two-stroke free piston linear engine, linear generators and air compressors. Each parameter of fuel input heat, equivalence ratio, spark timing delay, electrical resistance and air gap length were set up to identify the combustion characteristics and to examine the performance of linear engine. The linear engine was fueled with propane. In the course of all linear engine operations, intake air was inputted under the wide open throttle state. Air and fuel mass flow rate were varied by using mass flow controller and these were premixed by pre-mixing device. Subsequently, pre-mixture was directly supplied into each cylinder. Through the experiments, some facts that the generating power was induced differently at each operation conditions of linear engine were confirmed. In the linear engine, ultimately, piston frequency, velocity and combustion characteristics were different at each operating conditions. As a result, the piston frequency was and maximum generating power was 57.2 Hz and 111.3 W under the operating condition of 1.0 of equivalency ratio, 1.5 ms of spark timing delay, 30 Ω of electric resistance and 1.0 mm of air gap length, respectively.