In the framework of Thomas-Fermi equation, we have examined the properties of neutron star by assuming the existence of a new intermediate force which is composition dependent. We have found that the structure, size and mass of neutron star are affected by the strength and range of this new force. In the ultrarelativistic limit, we have also confirmed that Chandraseknar mass, $M_{ch}simeq(1-alpha)^{-3/2}{m_{pl}}^3/m^2$ is determined by the constants of classical physical laws, which take part in the selfgravitating processes on neutron star as well as the constant of hypothetical fifth force. In the experimental limits of the fifth force, the changes of size and mass of a neutron star are in the order of strength parameter $alpha$.