In this study, an attempt is made to investigate the rheological behavior and thermo-rheological properties of PVC in the presence of new tannin based thermal stabilizer. Tannin based epoxy resin has been used as nonmetallic thermal stabilizer additive to study its effects on the rheological behavior of PVC. Frequency sweep tests were applied for monitoring and evaluating the rheological properties of PVC formulations with different levels from this derivative (0, 5, 10, and 20) parts per hundred ratio (phr) using a parallel plate rheometer at 165 A degrees C. The general results indicate that the adding of tannin epoxy resin to PVC can provide enhanced dynamic thermal and process stability and improved the rheological properties. In these formulation systems, the rheological properties of PVC with tannin epoxy resin were more closed to that of PVC without plasticizer so that the plasticization effect of tannin epoxy resin was at very limited level. The rheological properties, such as storage modulus, complex viscosity and damping factor proved simultaneously that the PVC stabilized with tannin derivative exhibits excellent rheological behavior and melt thermal stability properties which were very comparable to that of PVC stabilized with 2 phr Reapak B-NT/7060; a commercial type thermal stabilizer.