Abstract: Annular Hypersonic Low-Temperature (HYLTE) nozzle arrayis the gain generator assembly in cylindrical chemical lasers. In thispaper, double cubic and Witozinsky curves are applied to the design of HYLTEnozzle convergent contour, and two kinds of HYLTE nozzles are designed. Based on 3D Navier-Stokes equations and the realizable k-\varepsilon model, the multi-species reacting flow field of the annular HYLTEnozzles is calculated. The numerical simulation results show that bothcontraction curves can prevent the separation of boundary layers, and thedifference of fluid dynamics parameters in the divergent section is negligible.However, with the nozzle designed by Witozinsky curve the fluid velocityis higher as compared with that designed by double cubic cueve, thus the recombination of F atomis slower, and the mass rate of F atom is about 5\% higher. It can beconcluded that cylindrical chemical laser with a convergent section nozzledesigned by Witozinsky curve works with a higher efficiency.