In this paper, new rheological models for castor oil are proposed. The aim of this study was to find a linear, exponential, and polynomial dependence between shear stress and shear rate of castor oil using tree equation. Equation constants , A, B, and C were determined by fitting linear, exponential, and polynomial. The castor oil has been evaluated using a Haake VT 550 Viscotester developing shear rates in the range of 3-120 s-1 and measuring viscosities from 104-106 mPa·s when the HV1 viscosity sensor is used. The castor oil of the dependence shear rate decreases with increasing shear stress at a constant temperature.