Ionic liquids (ILs) are emerging as a new family of environmentally benign solvents alternative to the conventional solvents for most catalytic reactions due to their nonvolatility. In such applications, thermal stability and solubility are vital for the selection of a suitable IL solvent for a particular reaction. In this work, the thermal stability of three commonly used imidazolium ILs (bmim[BF4], bmim[PF6], bmim[Tf2N]) was studied with both nonisothermal and isothermal thermogravimetric analysis (TGA). The decomposition kinetics indicated the relative anion stability for imidazolium based ILs was Tf2N > PF6 > BF4. In addition, the solubility data of three organic compounds (methanol, ethyl acetate, and benzene) in ILs were specified by the binary vaporliquid equilibrium (VLE) at elevated temperatures. The results indicated bmim[Tf2N] was the best solvent for the organics investigated. For the same IL, the solute with a higher polarity tends to possess a lower activity coefficient. The activity coefficients of the organic compounds agreed well with the nonrandom two-liquid (NRTL) model.