As　an　established　method　to　analyse　the　thermodynamic　process　inside　the　cylinder,　the　p-V　diagram　can　identify　typical　faults　such　as　leakages　through　the　sealing　rings　and　self-acting　valves,　loosening　and　fluttering　of　the　vales,　etc.　However,　the　installation　of　the　pressure　sensor　within　the　cylinder　for　recording　the　p-V　diagram　may　lead　to　degradation　of　the　cylinder　integrity,　and　hereby　potential　leakage　and　lowered　strength　of　the　cylinder.　This　paper　presents　a　new　non-destructive　method　for　fault　diagnosis　of　the　reciprocating　compressor　by　measuring　the　piston　rod　strain,　from　which　the　p-V　diagram　was　transformed.　An　algorithm　for　reconstruction　of　the　p-V　diagram　was　proposed　based　on　the　key　feature　points　on　the　piston　rod　load　curve　that　reflect　the　opening　and　closing　events　of　the　compressor　valves.　The　reconstruction　method　was　validated　by　comparing　the　calculated　p-V　diagrams　with　the　experimental　results.　The　reconstructed　p-V　diagrams　were　further　used　for　fault　diagnosis　of　the　reciprocating　compressors,　with　which　the　acoustic　emission　method　was　integrated.　The　results　show　that　this　method　can　easily　monitor　the　working　conditions　and　identify　whether　and　where　leakage,　fluttering　and　delayed　closing　of　the　valves　occur,　which　indicates　that　this　method　can　be　utilized　as　a　powerful　tool　of　non-destructive　condition　monitoring　and　fault　diagnosis　of　the　reciprocating　compressors.　©　Published　under　licence　by　IOP　Publishing　Ltd.