Abstract: The jet singlet oxygen generator (JSOG) is an efficient energy donor for a chemical oxygen-iodine laser (COIL). Using the trial-solution method under specific boundary conditions, the diffusion equations were derived of chlorine, singlet oxygen, and total oxygen in gas and liquid phases. The analytical solutions for the utilization of chlorine and the yield of singlet oxygen were obtained, which agree with the experimental results and are helpful for further improvement and optimization of the JSOG.