A simple model for photoinitiated F2/H2 chain reaction lasers is presented, which replenishes some deficiencies of Kerber’s model. The compatibility of time coordinates between the laser flux equations of V-R transitions and the kinetic rate equations has been solved. By using Gear’s automatic integration method, satisfactory numerical results have been obtained. The effects of prereaction of F2/H2 mixtures, of O2 content and of photoinitiator on pulsed HF laser performances are presented.