The effects of temperature and pressure nonuniformities at evaporation on the properties of liquid-gas interface are studied by molecular dynamics (MD) simulation and thermodynamic perturbation method on the basis of the van der Waals theory of capillarity. The structure and properties of the interfacial layer of equilibrium and nonequilibrium Lennard-Jones (12-6) systems are investigated. The surface tension, the two-particle distribution functions, the density fluctuation correlation lengths, and the evaporation coefficients are calculated using MD simulation. It is shown that the presence of the temperature gradient at the interface due to evaporation leads to reduction of the surface tension. The results of MD simulations are in agreement with the results of thermodynamic approach.