Water content of ethylene gas in equilibrium with hydrate and water phases were determined at temperatures between 274.15 up to 292.75 K and pressures between 593.99 to 10.543.18 kPa. The experimental and theoretial enhancement factor(EF) for the water content of ethylene and the fugacity coefficients of water and ethylene in gas phase were determined and compared with each other over the entire range of pressure carried out in this experiment. In order to get the theoretical enhancement factors, the modified Redlich-Kwong equation of state was used. The Peng-Robinson equations and modified Redlich-Kwong equations of state were used to get the fugacity coefficients for ethylene and water in the gas phase. The results predicted by both equations agree very well with the experimental values for the fugacity coefficients of the compressed ethylene containing small amount of water, whereas, those of water vapor in the ethylene rich gas do not. The maximum value of the water content of the ethylene in this work was 0.0029 mole fraction at 4,479.25 kPa and 290 K which may be near the critical locus of the mixture of ethylene and water