Gas-liquid phase equilibrium data of methyl chloride-n-hexane binary system was measured by phase equilibrium apparatus in which liquid circulates. Experimental data was regressed and Binary parameter of methyl chloride and n-hexane kij was calculated by SRK state equation，which is 0.05. It was found that liquid phase constitute of methyl chloride in n-hexane decreases with the increase of temperature，but increases with the increase of pressure.The average standard deviation of CH ₃Cl gas constitute was 1.076 4% and the average standard deviation of pressure was 0.985 4%, which explain SRK state equation is accurate in regressing gas-liquid phase equilibrium data.Basing on it, gas-liquid phase equilibrium data of methyl chloride-n-hexane binary system in all concentration range were calculated. p-x,y phase graph at 25,30,40,50 ℃ was obtained.