Magnetic Abrasive Finishing (MAF) is relatively a new finishing technique which employs the magnetic force for finishing. In this paper, the influence of the magnetic flux density on the finishing pressure and the finishing efficiency during finishing is analyzed. With the cylindrical magnetic finishing apparatus developed by the author, a series of experiments on finishing the cylindrical surfaces of nonferromagnetic materials and ferromagnetic materials are carried out. To solve the problems of low finishing efficiency and abrasive particles escaping easily because of lack of finishing pressure during finishing nonferromagnetic materials, a new method of increasing the finishing pressure by using the “pressure-increasing bag” in the finishing system is put forward. A lot of comparative experiments on finishing nonferromagnetic materials with the “pressure-increasing bag” and without the “pressure-increasing bag” are performed. Under the same experimental conditions, the amount of diameter-reduction d is increased from 1μm to 1.88μm and the surface roughness is improved from Ra0.315μm to Ra0.250μm by using the “pressure-increasing bag”. The results show that the finishing pressure is increased obviously and the MAF efficiency of finishing nonferromagnetic materials is improved dramatically by using the “pressure-increasing bag”.