In order to investigate the heat and mass transfer characteristics, the absorption experiment of water vapor into the solution was carried out by using a static-pool type absorber. The aqueous lithium bromide solution with 1,3-propanediol, which has been previously developed for the air-cooled absorption chiller, was treated with n-octanol and 2-ethyl-1-hexanol. The concentrations of the absorbent were 54.5 and 67.8 wt%. The mass transfer enhancement by additives was clearly observed with increasing the additive concentration. Surface tensions of the water + lithium bromide + 1,3-propanediol system with n-octanol and 2-ethyl-1-hexanol were measured at various additive concentrations. The absorption behavior of the solutions was discussed qualitatively along with the surface tension data.