In order to solve the camber problem of intermediate slab in a domestic conventional hot rolling mill, a three-dimensional elastic-plastic dynamic model was built through finite element method to quantitatively calculate the influence of lateral flow factors in different entry thicknesses, reductions, reduction ratios differences on both sides and width factors. Thus, the extending difference at outlet of intermediate slab in length was transformed into thickness difference on both sides by the results, and then the tilting value of roll gap reduction to control the camber was calculated. Based on the above results, the camber control model of intermediate slab in rough rolling was established. The practical application on the rough rolling mill obtained a decent control effect, and it proved that this model had a high accuracy.