The closure of a turbulence field is a longstanding fundamental problem,while most closure models are introduced in spectral space.Inspired by Chous quasi-normal closure method in spectral space,we propose an analytical closure model for isotropic turbulence based on the extended scale similarity theory of the velocity structure function in physical space.The assumptions and certain approximations are justified with direct numerical simulation.The asymptotic scaling properties are reproduced by this new closure method,in comparison to the classical Batchelor model.