A　preliminary　experimental　investigation　of　a　free　piston　expander-linear　generator　(FPE-LG)　prototype　was　presented.　The　aim　of　developing　this　FPE-LG　prototype　was　to　applied　it　in　a　small　scale　organic　Rankine　cycle　(ORC)　system　for　vehicle　waste　heat　recovery,　which　can　convert　the　thermodynamic　energy　of　working　fluid　into　electric　energy.　Technical　feasibility　of　prototype　using　a　newly　developed　valve　train　was　verified.　The　phase　matching　of　different　cam　plates,　free-piston　motion　characteristics,　as　well　as　the　power　output　of　FPE-LG　was　identified　based　on　the　compressed　air　test　bench.　Experimental　results　showed　that　FPE-LG　can　run　stably　under　the　condition　of　high　inlet　pressure.　The　cycle-to-cycle　variations　of　velocity　at　the　reference　position　and　the　cycle-to-cycle　variations　of　displacement　at　top　dead　center　and　bottom　dead　center　can　be　ignored.　The　peak　velocity　of　free-piston　was　close　to　1.2　m/s　when　the　intake　pressure　was　0.2　MPa　and　working　frequency　was　2.5　Hz.　The　valve　timing　and　intake　pressure　had　an　important　influence　on　the　motion　characteristics　of　free-piston　and　power　output　of　linear　generator.　Decreasing　the　exhaust　duration　angle　or　increasing　the　intake　duration　angle　can　improve　the　stability,　symmetry　of　free　piston,　reduce　cycle-to-cycle　variation　of　free-piston　motion　and　improve　the　power　output　obviously　when　other　parameters　were　constant.　The　maximum　peak　power　output　was　about　19.0　W　when　inlet　pressure　was　0.19　MPa　and　working　frequency　was　2.5　Hz.　©　2017,　Chinese　Society　of　Agricultural　Machinery.　All　right　reserved.