In this paper the density and temperature dependencies of surface tension are investigated. Using the Lennard-Jones (12, 6), as an effective pair interaction potential, a linear expression is derived for isotherms of g /r2 versus r2 for some normal and ChloroFluoroCarbons (CFCs) fluids, where g is surface tension and r=1/v is molar density. The linearity behavior of the derived equation is well fitted onto the experimental data of surface tension for monatomic, diatomic, nonpolar, polar, hydrogen-bonded and chlorofluorocarbons. In addition, the temperature dependence of surface tension for 20 different fluids is examined, in which the contributions of both terms of the average effective pair potential to theg are determined. For all liquids investigated in this work, surface tension increases with density except for water. The surface tension of water for isotherms within 280-300 K decreases with density, whereas increases within the range of 310-320 K.