A V-model unstable optical resonator is designed, and the rule of the output spectrum of continuous wave hydrogen fluoride (HF) laser is discussed on the condition of different oxidant excess indexes. Spectral lines corresponding to wavelength over 2.87 μm, such as 2P8 and 2P9, are obtained efficiently under appropriate reaction formula and optical resonator parameters. We can partly regulate the distribution of HF laser output spectrum by adjusting the combustor oxidant excess index and controlling the amount of free fluoride atom lasing reaction. The output power of laser is closely related to the gain coefficient. The maximal output power of a single spectral line is determined by its maximal gain coefficient, while the maximal output power of the laser depends on the maximal value of the sum of all spectral lines gain coefficients.