As group contribution method is easy to apply and has a wide application range,current study has developed this model to predict flammability limit of hydrocarbons mixed with inert gas using the Marrero/Gani group contribution method,which is significative to the safe application of hydrocarbons in the ORC system.The whole modeling process is divided into two parts: pure compound prediction and mixture prediction.The contribution factors of inert gases and dilute concentration were first introduced in the group contribution method.Moreover,the respective 95％-confidence interval of the mixture based on linear superposition method has been proposed in the developed group contribution model to improve the safety coefficient.For CO2 as inert gas,the average relative error and correlation coefficient are 5.34％ and 0.88 for lower flammability limit while 6.99％ and 0.95 for upper flammability limit.For N2 as inert gas,the average relative error and correlation coefficient are 7.47％ and 0.84 for lower flammability limit while 6.68％ and 0.97 for upper flammability limit.Most importantly,this group contribution method has extended the application range to make up the shortcomings of other flammability limit prediction methods aiming at hydrocarbon and inert gas mixtures and proposed the uncertainty analysis to provide reliable prediction range.