A series of molten salts EMIm(HF)(n)F's with different it values has been synthesized by the reaction of EMImHF(2)) and anhydrous hydrogen fluoride. The salts contain ENIm cation and some oligomeric fluorohydrogenate anions, (HF)(n)F-, of which the fraction changes with the change of n. A phase diagram of EMIm(HF)(n)F's (n = 1.0-2.6) has been constructed which suggests the presence of the stoichiometric compounds, EMIm(HF)(1.5)F and EMIm(HF)(2)F, in this range. Compared to the EMIm(HF)(2.3)F previously reported, EMIm(HF)(n)F's (it = 1.8-2.0) possess wider liquid temperature ranges because of their similar melting points and superior thermal stabilities at elevated temperatures. The electrochemical windows of EMIm(HF)(n)F's (n = 1.0-2.6) falls in the range of 2.9-3.4 V. The conductivity of EMIm(HF)(n)F's (n = 1.0-2.6) increases with the increase of n.