Abstract: Oscillatory rheometer was used to investigate the effects of some synthetic sweeteners (Aspartame, Acesulfame k, Cyclamate and Neotame) on rheological behavior of High Methoxyled Pectin (HMP) in dilute solutions. The concentration of these sweeteners were 0.1, 0.2% w/v for Aspartame, Acesulfame-k and Cyclamate and 0.001, 0.002% w/v for Neotame. We used various equations such as Huggins, Kraemer, Tanglertpaibul and Rao equations to assess the best model for determination intrinsic viscosity of HMP. The results showed that the values obtained for intrinsic viscosity were different by the equation used for estimation the intrinsic viscosity. We found 1-1/ηrel versus concentration plot as the best model. Addition of any of these four sweeteners had no significant effect on intrinsic viscosity of HMP in solutions.