This study is concerned with measurements of vapor-liquid equilibrium (VLE) for 1-butene/1, 3-butadiene/DMF and 1-butene/1, 3-butadiene/DMF with salt. A set of experimental apparatus has been established to measure the VLE of the two systems. Data of T-P-x-y at middle pressures have been obtained. The coincidence of experimental and calculated values, and the consistency of thermodynamics show that the experimental results appear accurate and the experimental apparatus is reliable. In contrast to using DMF only, DMF with salt is a better solvent and increases the relative volatility of 1-butene to 1, 3-butadiene. The UNIFAC models for the two systems have been set up, and a good agreement between the predicted and the experimental is achieved.