To　further　understand　single-piston　free　piston　expander　linear　generator　(FPE-LG),　a　novel　FPE-LG　prototype　had　been　established　for　small　scale　organic　Rankine　cycle(ORC)　waste　heat　recovery　system.　The　single-piston　FPE-LG　can　operate　continuously　and　stably　based　on　the　compressed　air　test　bench,　which　indicates　that　the　working　principle　of　single-piston　FPE-LG　is　feasible.　The　effects　of　intake　pressure,　piston　stroke　length,　external　load　resistance　and　intake　duration　on　the　motion　characteristics　of　the　single-piston　FPE-LG　are　investigated,　and　the　results　show　that　the　variation　trend　of　piston　displacement　and　velocity　exhibits　a　regular　sinusoidal　fluctuation.　Relative　high　velocity　is　near　the　dead　centers　and　peak　acceleration　is　usually　obtained　when　the　piston　arrives　at　left　dead　center(LDC)　or　right　dead　center(RDC).　By　using　the　variable　length　of　piston　stroke　to　improve　output　power　is　feasible.　But　the　change　of　piston　stroke　has　little　effect　on　the　peak　piston　velocity　and　the　peak　pressure　of　cylinder.　The　peak　piston　velocity　and　piston　stroke　utilization　ratio　(η)　increase　with　the　external　load　resistance.　When　the　external　load　resistance　increases　from　20　Ω　to　80　Ω,　the　peak　piston　velocity　and　η　increase　from　0.56　m/s　and　58.26%　to　0.84　m/s　and　78.42%,　respectively.　Increasing　intake　duration　is　beneficial　to　obtaining　higher　piston　velocity,　piston　stroke　utilization　ratio　and　output　power.　The　peak　output　power　increases　from　13.87　W　to　37.40　W　when　the　intake　duration　changes　from　20　ms　to　40　ms.　©　2019,　Editorial　Board　of　Journal　of　Harbin　Institute　of　Technology.　All　right　reserved.