This work presents an application of a reduced chemical kinetic mechanism using Computational Singular Pertubation (CSP) based on the significant indices of the modes on evolution of species and the degree of participation of reactions. This approach enabled us to reduce the mechanism of Yang and Pope to 22 reversible reactions. In this study, the tabulation of ignition delays has been made using a Yang and Pope mechanism, GRI 3.0 and reduced mechanism; the results obtained showed a good agreement among the three mechanisms. “Modele Intermittent Lagrangien” (MIL) has been used to calculate the chemical source term of the transport equation of the species. The calculation of this unclosed term requires a library of ignition delays which takes into account a detailed chemical kinetic mechanism, a probability density function (PDF) of the mixture fraction which is presumed by a beta distribution. The scalar variance, one of the key parameters for the determination of the presumed beta function, is obtained by solving its own transport equation with the unclosed scalar dissipation rate modeled using either an algebraic model or a transport equation. All these models are introduced in the CFD SATURNE code and applied to simulate a turbulent CH4/H2/N2 jet flame (DLR Flame A) proposed by the German aerospace center. A set of comparisons is made; the results of simulations show a good agreement among the three mechanisms and also with the experimental data.