The paper describes a multistep chemistry, combustion-zone submodel for turbulent combustion simulation which can be used in the regime of flamelet combustion. The flowfield in the submodel is simplified by assuming a uniform strain rate across the flame structure as opposed to the variable strain observed in the corresponding boundary-layer solution. This assumption allows the decoupling of the momentum equation from the energy and species concentration equations, and, together with a series of coordinate transformations, the reduction of the system of governing equations to a set of reaction-diffusion equations which can be accurately and easily integrated. Study shows that the accuracy of the model can be greatly improved if an effective uniform strain rate instead of the imposed strain rate at the far field is used. We develop an expression for the effective uniform strain rate as a function of the flow-imposed strain and the adiabatic flame temperature. Results obtained over a wide range of strain rates show that the results of the uniform strain-rate model agree well with those obtained using the boundary-layer approximation in terms of the steady-state flame structure and evolution of the burning velocity in response to a stepwise change in strain rate for both premixed and diffusion flames. It is also shown that the uniform strain-rate model with reduced chemical kinetics is able to produce the extinction S curve, steady-state profiles, and a transient response which are close to that of the exact solution. The importance of the dynamics of flame-flow interaction is shown in the paper by comparing the actual response of a flame to sudden variations in strain rate with the quasisteady response implied in the ＇＇flamelet library＇＇ approach. It is shown that the latter could lead to errors in the prediction of burning velocity.