The influences of wet ultra-fine grinding parameters on the rheological behavior of pyrite–heptane slurry in a laboratory stirred media mill were investigated with solid concentration, dispersant dosage, grinding time and carbon numbers of organic acid as dispersant. The results reveal that when the solids concentration is increased from 64wt% to 79wt%, the rheological behavior of slurry with 1wt% of stearic acid transforms from Bingham characteristic to the pseudoplastic one with a yield stress. The Casson model fits well for the experimental data. And the apparent viscosity of the pyrite–heptane slurry increases exponentially with increase solid concentration at a given shear rate. The increase of viscosity is propitious to reduce the particle size of pyrite. When the solid concentration is 64wt%, stearic acid is superior to octadecanol for the reduction of the slurry viscosity, and the slurry with 1wt% of stearic acid possesses the best flowability. The extrapolated Bingham yield stress with dispersant almost stays constant when the dosage is over 2wt%. Besides, the rheological behavior and particle size are also related to the grinding time and carbon numbers of organic acids as dispersant.