The influences of the concentration of HF molecular and the consumption of the working medium on the laser pulse energy are studied. The laser pulse energy decreases obviously with the increasing of the concentration of HF molecular in the laser, due to the reabsorption of the HF molecule on laser and the strong relaxation effect of the HF molecule on the excited molecules. The laser pulse energy decreases about 1.15% with the increasing of the concentration of HF molecular for 10 15 cm -3. In addition, each excited HF molecule can emit 0.8 photons, the dissociation rate of SF6 molecules in the discharge region is about 1%, and the consumption of the working medium is small for a single discharge process and the consumption is about 1/(2×10 5) of the total gas amount. The experimental results show that the laser pulse energy is affected seriously by the HF molecular concentration, but weakly by the medium consumption. With the add of the molecular sieves in the laser chamber, the HF molecular concentration is maintained at a level of 1.8×10 15 cm -3, and the laser pulse energy decreases about 10% under the coaction of two factors.