Numerical modeling of turbulent-reacting flow field in supersonic combustors is presented. When flow field and chemical kinetics with differing time scales need to be solved simultaneously, explicit treatment of all conservation terms with reaction chemistry results in stiff equations and has a tendency to degrade the performance of numerical method. A method of preconditioning, in which the conservation equations in conjunction with chemical source terms alone is treated implicitly. Such a method has the advantage of both explicit and implicit methods. A code was developed using above method and tested successfully for a supersonic combustor configuration. © 2007 World Scientific Publishing Company.