In this paper the laser linewidth without rotating wave approximation is studied by keeping the ratio of the atomic natural decay rate to the radiation frequency to two orders.It is shown that while the linewidth is confined to the Schawlow-Townes formula,the non-rotating wave terms would cause the linewidth to increase since the non-rotating wave terms decrease the average photon number.The degree of increasing in linewidth depends not only on the square of the ratio of the atomic natural de-cay rate to radiation frequency,but also on the average photon number in rotating wave approxima-tion.The influence of the non-rotating wave terms on the laser linewidth is much larger than on the photon number fluctuations.