In this paper, a new method of estimating critical parameters (P C , V c , T c ) for pure substances is presented based on saturated liquid PVTdata under low pressures. To prove the accuracy of this method the critical parameters of fifty substances (including strongly polar and associated compounds, such as ammonia, methanol, ethanol, etc.) were calculated and compared with experimental data. The calculated results show that the new method is fairly fitted in the experimental data with the percentage average absolute deviation (AAD%) 0.64% (T c ), 0.92% (P c ) and 0.96% (V c ) respectively in the investigated range.