A　single　cylinder　free　piston　expander-linear　generator　(FPE-LG)　used　for　organic　Rankine　cycle　(ORC)　waste　heat　recovery　system　is　developed　to　improve　the　energy　efficiency　of　the　internal　combustion　engines.　FPE-LG　can　operate　continuously　and　stably　under　the　condition　of　high　driven　pressure,　which　indicates　that　the　working　principle　of　single　cylinder　FPE-LG　is　feasible.　The　effects　of　driven　pressure　and　external　load　resistance　on　the　output　characteristics　of　single　cylinder　FPE-LG　are　investigated　through　experiment.　The　experimental　test　results　show　that　the　power　output　of　FPE-LG　exhibits　a　regular　sinusoidal　fluctuation,　and　the　peak　power　output　can　reach　58.7　W　when　the　driven　pressure　is　0.6　MPa　and　the　external　load　resistance　is　50　Ω.　The　increase　in　driven　pressure　can　increase　the　RMS　voltage　and　peak　current　significantly.　However,　it　has　little　effect　on　the　power-electric　conversion　efficiency　of　FPE-LG.　When　the　external　load　resistance　is　less　than　60　Ω,　the　power-electric　conversion　efficiency　η　of　FPE-LG　increases　from　13.4%　to　24.7%　with　the　increase　in　external　load　resistance.　When　the　external　load　resistance　is　60　Ω,　actual　expansion　work　(AEW),　WAEW,　of　the　single　cylinder　FPE-LG　is　the　largest　and　the　power-electric　conversion　efficiency　is　the　best.　The　continuous　increase　in　the　external　load　resistance　value　has　little　effect　on　WAEW　and　η.　©　2018,　Editorial　Board　of　Acta　Armamentarii.　All　right　reserved.