The lithium bromide + lithium iodide + 1,3-propanediol + water (LiBr/LiI mole ratio = 4 and (LiBr + LiI)/HO(CH2)(3)OH mass ratio = 4) solution was selected as the potential working fluid for an air-cooled absorption chiller, and its basic four thermophysical properties were measured. The solubilities were measured in the range of absorbent (LiBr + LiI + HO(CH2)(3)OH) concentration from 70.0 mass % to 77.8 mass %. The vapor pressures were measured in the ranges of temperature and absorbent concentration from 339.75 K to 444.35 K and from 55.0 mass % to 80.0 mass %. Both the densities and viscosities were measured in the temperature and concentration ranges of 283.15 K to 343.15 K and 25.0 mass % to 75.0 mass %, respectively. The individual data set was correlated with a regression equation with high accuracy. The absorption chiller using the new solution as a working fluid is expected to have a wide operation range without the danger of crystallization, which is the critical problem in constructing an air-cooled absorption chiller.