The influences of Compton scattering to temporal evolution of plasma density in femto-second light filaments are studied by using Compton scattering model, plasma time-section model and number computing means. A new mechanism that the electron crest density in the plasma is changed by Compton scattering is proposed. The amended dynamic equations of charged particles are given out, and the equations are computed by numerical method. The results show that the time the plasma need to be conductive is reduced by Compton scattering, the increasing of electron density in the ionization area is in quasi-saturated state, the electron densities in the ionization decreased area is almost constant, and the differences of the ionization contribution rates of different pulses are very little. The O2 ionization contribution rate decreases along with the increase of the light intensity of the pulse section and the O2 ionization contribution rate is finally overstepped by the N2 contribution rate. The electron crest density increases in plasma channel and the channel lifetime is extended as well. Under the same crest density, the increases of the electron crest density produced by the long or short pulses are almost the same, and the increases are rather smaller after scattering.