In this paper some of rheological properties of bamboo charcoal polyester (BC-PET) are presented. The BC-PET is derived from PET modified through commix with bamboo charcoal master batch. The additive content of blends ranged between 0% and 10%. Rheological measurements were effectuated with a Brookfield viscometer (RVDV-II+Pro). The results showed that molten BC-PET exhibited shear thinning fluid, these were verified with some rheological models. Non-Newtonian index decreased significantly and structural viscosity index increased obviously with the master-batch content increased, but the viscosity was stable in the shear rate range of spinning (γ=103-104s-1), so decreased the temperature was beneficial to spinning.