A branch reaction of high density polyethylene initiated by Dicumyl peroxide in an internal batch mixer was used to investigate the rheokinetics on homogeneous polymer reactions in melt state under strong flow environment. The effect of shear strength on the reaction process was focused. A real conversion of reaction was put forward from the rheological measurement, i.e., the torque of mixer. A comparison of the reaction conversion from experiment and the chemical kinetic model gave a flow dependent combination rate parameter. A rheokinetic equation was therefore obtained which is in a good accordance with the theoretical prediction by Fredrickson and Leibler [4]. The rheokinetic equation was further verified by a simplified nonisothermal two-dimensional numerical simulation which incorporates macro-convection effect. (C) 2009 Elsevier Ltd. All rights reserved.