The vapor-liquid equilibrium data of n-propyl alcohol （1）-n-propyl acetate(2) system having similar physical properties and showing the azeotropic composition x₁=0.63 mol fraction at 94.2 ℃ were experimentally measured under atmospheric pressure. The experimental data were proved to be correct by the Herington test method. In order to eliminate or shift the azeotropic composition of the system, three kinds of additives such as LiCl, CaCl₂ and Urea were added into the system in the extent of saturation and then the new vapor-liquid equilibruim data were obtained, and the effect of each additive was investigated. By adding additive the azeotropic points were shifted to some extent, but not disappeared in any case. For the case of LiCl the salt effect shows remarkably large, the next of CaCl₂, and Urea shows the smallest effect. In addition of the measurement, the solubility of LiCl, CaCl₂ and Urea in the system were determined at their respective boiling points. The salt effect parameter(k₃) calculated from experimental data by aid of the Furter equation represents a good coincidence with the experimental results.