Biodiesel offers better combustion efficiency, lower sulfur content and aromatic compounds, higher cetane numbers than diesel fuel, biodegradable and renewable properties that are not possessed by conventional fuels such as diesel fuel. This study aims to study the esterification process of Cotton Seed oil using liquid ionic catalyst 1-Butyl-3-MethydidazoliumHexafluorophosphate (BMIM-PF6) which is simulated by MATLAB 2014 software to compare the kinetic model and the reaction order between the experiment and simulation results with 3% liquid ionic catalyst , then test the validity of the reaction kinetic models. The validation results of reaction kinetic models for experiments and simulations provide an adjacent correlation value, that is R2 = 0.99526, with the reaction speed value (k) based on experimental data are 0.003815 and 0.0038 for the simulation data. Based on the simulation results, the proper reaction order for this esterification reaction is the first order reaction equation with a value of R2 = 0.99526, while the second order reaction gives the value R2 = 0.89453. The reaction kinetics parameters obtained from the experimental results are A = 0.012 and -Ea = -0.437, while the reaction parameters of the simulation are A = 1.0384 and -Ea = -89.5.