Buildup of magnetic mineral particles on matrices determines the saturated deposit volume of minerals, which is of great importance in the high gradient magnetic separation (HGMS) systems. In this paper buildup of fine weakly magnetic minerals on the matrix is studied with a force equilibrium model. Elaborate rules of particle buildup on the matrix are presented. An imaginary sector ring is used to approximately quantify the volume of saturated particle buildup. The influence of the particle size, magnetic induction, fluid viscosity and velocity as well as matrix size on saturated particle buildup is investigated and discussed. With the same matrix size, the saturated buildup volume decreases with the decrease of the particle size, applied magnetic induction and increase of the fluid viscosity and velocity. The saturated buildup volume normalized by the matrix volume, and the ratio of particle deposit volume to the matrix volume (Vd/Vm) decreases with the increase of the matrix size. Under the same matrices packing fraction, the total mineral deposit volume, when adopting small size matrices, is larger than that when adopting large size matrices. Only small size matrices can be used for recovery of minerals in size of several micrometers. Based on performed analyses, the ore feeding time in a cycle for a cyclic HGMS system and the rotation speed of the swivel for a continuous HGMS system under different circumstances are also discussed.