In　order　to　study　the　effect　of　operating　parameters　on　the　heat　release　models　calculation　result　of　compressed　natural　gas　(CNG)　engine　and　confirm　the　models　application　conditions,　Gatowski　et　al　model,　Apparent　heat　release　model　and　R-W　model　were　used　to　calculate　heat　release　rate　and　mass　fraction　burned　based　on　the　cylinder　pressure　and　crank　angle　data　measured　from　a　spark　ignition　CNG　engine.　The　effect　of　engine　operating　parameters　on　the　calculate　results　of　different　heat　release　models　were　discussed.　The　results　show　that　the　difference　of　heat　release　rate　and　mass　fraction　burned　calculated　between　Apparent　heat　release　model　and　R-W　model　is　not　obvious,　which　indicates　that　the　two　models　can　be　in　common　use.　The　three　models　are　affected　slightly　by　ignition　advance　angle　and　excess　air　ratio.　Difference　among　three　models　calculation　results　is　not　huge　with　small　throttle　opening.　Compared　with　the　other　two　models,　the　calculation　results　of　Gatowski　et　al　model　are　affected　significantly　by　engine　speed.　The　three　models　substitutes　mutually　under　the　condition　of　small　throttle　opening　or　high　engine　speed.　Gatowski　et　al　model　is　more　accurate　and　suitable　for　slow　engine　speed　compared　with　the　other　two　models.