A simple and semiempirical rheological equation of state was developed to describe and predict the steady-state shear viscosities of hollow sphere loaded polymer melts as functions of temperature, shear rate, and composition of hollow sphere. High density polyethylene (HDPE) was used as a matrix polymer and steady-state shear viscosities of various compositions of HDPE/hollow sphere polymeric composites were measured at various temperatures. The destruction of hollow spheres was observed during viscosity measurement. The proposed model successfully predicted the rheological behaviour of HDPE/hollow sphere systems. It is a simplified algebraic form with a few parameters and gives a great advantage for practical application.