A high gradient magnetic cleaning process is favored by several branches of industry for the high purification of various technological fluids involving magnetic(ferro, para, or diamagnetic) particles. This paper presents a theoretical study about the effects of the parameters of a magnetic filtration system on the fluid velocity to be chosen. A model is presented to estimate the optimum filtration velocity needed to satisfy a predefined filter performance. The model is applicable for magnetic filter systems with packing fractions of up to 0.62 and for fluids containing magnetic particles. It is essentially based on the balance of moments acting on particles captured and accumulated in the magnetic filter. The boundary layer approach is used in the development of the model. The results indicate that the optimum filtration velocity depends on the properties of the fluid and on the parameters of the filter system. Model predictions and experimental data given in the literature are in a good agreement.