The effect of initial pressure on the output characteristics of the 46.9 nm laser is investigated when the Ar-He mixture with a pressure ratio of 8∶1 is filled into the capillary. By measuring the pressure range of 46.9 nm laser produced by Ar-He mixture, and the corresponding laser intensity and spot shape information at each pressure, the relationship between laser output characteristics and initial pressure of Ar-He mixture is summarized. Then, the influence of the initial pressure of Ar-He mixture on the laser spot is analyzed from the point of view of the plasma column, and the reason for the change of the output characteristics of 46.9 nm laser caused by the initial pressure of the Ar-He mixture is obtained. The above research on the laser characteristics is beneficial to improve the laser amplitude and change the shape of the laser spot.