Abstract: Magnetic field was employed in the absorption course of ammonia-water absorption refrigeration. The numerical model of falling film absorption outside vertical tube with ammonia-water in the presenting of magnetic field was set up. The macroscopic magnetic force was added in the equation of momentum. In the process of modeling, the variation of falling film thickness, the variation of physical characteristics of ammonia-water and the convection in the direction of the film thickness were considered. The distribution of temperature and concentration and temperature of falling film were obtained within 0-3T of magnetic induction intensity by numerical solving. The results show that the absorption heat, the absorption mass, the mass transfer coefficient increased with the increase of magnetic induction intensity. The falling film absorption with ammonia-water could be strengthened to some degree by external magnetic field.