The influence of air turbulence on the long-range filamentation of femtosecond laser pulses has been numerically investigated. Simulations are performed for different parameters of air turbulence and laser pulses. Simulation results indicate that the diameter of filaments formed by free propagated fs laser pulse can be widened to mm level under air turbulence. However, the widening effect can be suppressed if the propagating distance before the on-set position of filamentation becomes shorter. The reduction of non-linear focal length can be realized by pre-focusing of the laser pulse or increasing of the laser intensity. The effect of the inner scale of air turbulence on the filamentation has also been studied.