The propagation of femtosecond laser pulse in the air containing a small amount of oxygen molecule in excited state is investigated by numerically solving the propagation equation, and the numerical results in both normal and low atmospheric pressures are compared. The numerical simulation results show that when the air contains excited molecules, it will affect the propagation process of the laser pulse. The bigger the proportion of the excited molecules is, the greater the influence of it on the time and spatial distribution of the laser intensity will be.