In the process of upgrading of bio-oil from the fast pyrolysis of biomass, there occur competitive reactions leading to the formation of heavy fraction, light fraction, and undesired fraction (water, gas, and coke) and simultaneously, the heavy fraction as intermediate product which further react to formation of the latter two fractions. Therefore, a lumping kinetic model, which contains four lumping species and five constants, was proposed to describe the process behavior of bio-oil hydrotreating. By the Simplex in non-linear multi-variable optimization, rate constants at different temperatures are obtained and the frequency factors and activation energies are calculated by using least square method. By using the assumed kinetic model, conversion and yields were calculated, which agree quite well with the experiment values.