Abstract: The relationship of the excitation coil of magnetic medium and the length of the separation space height of cycle type high gradient magnetic separator can greatly influence on the distribution of magnetic field intensity.The ratio of excitation coil length and height of the appropriate separation space can improve the recovery rate of magnetic minerals and reduce the energy consumption.The effect of long coil and short coil on the magnetic field strength，magnetic field gradient and magnetic force in the separation space was analyzed using ANSYS software，The results indicated that magnetic field intensity is not uniformity in sorting space of long coil，magnetic field intensity is uniformity in sorting space of short coil.When the background magnetic induction intensity is less than 1.0 T，long coil magnetic field gradient is greater than the short coil magnetic field gradient，when the background magnetic induction intensity is greater than 1.0 T，two kinds of coil magnetic field gradient will go stable.The background magnetic field intensity of the two coil is same，the magnetic force produced by long coil is greater than the short coil.Magnetic field produced by long coil is beneficial for low intensity magnetic minerals separation, while for short coil is beneficial for impurities removal of non-metallic minerals.The strong area of magnetic field intensity produced by the long coil is concentrated in the middle position of the cylinder column and the magnetic pole head of the distance separating space；the strong magnetic field intensity region generated by the short coil is concentrated in the intersection of the cylinder and the coil，the magnetic field intensity strength of the magnetic field nephogram of short coil separation space substantially uniform，similar with the change trend of the measured magnetic induction intensity.

Key words: Cycle type high gradient magnetic separator, Magnetic field intensity, Magnetic field gradient, Magnetic field force