Abstract. In this work, several multilevel decoupled algorithms are proposed for a mixed Navier-Stokes/Darcy model. These algorithms are based on either successively or parallelly solving two linear subdomain problems after solving a coupled nonlinear coarse grid problem. Error estimates are given to demonstrate the approximation accuracy of the algorithms. Experiments based on both the first order and the second order discretizations are presented to show the effectiveness of the decoupled algorithms.Key words. Fluid flow coupled with porous media flow, Darcy law, Navier-Stokes equations, Interface coupling, Multilevel algorithm, Decoupling, Linearization AMS subject classifications. 65F08, 65F10, 65N30, 65N551. Introduction. The coupling of incompressible fluid flow with porous media flow is an interesting but challenging topic. For describing the interactions of the fluid flow with the porous media flow, a coupled Stokes/Darcy or Naiver-Stokes/Darcy system is typically used as a macro-scale sharp interface model [2,3,6,8,9,12,13,14,16,17,18,19,20,21,23,24,25,34,35,37,40,41,42]. The coupled Navier-Stokes/Darcy model is composed of a nonlinear Navier-Stokes equations for fluid flow, a Darcy law equation for porous media flow, plus certain interface conditions for describing the interactions of the different types of flows. Numerical methods for this model [8,13,23,42] usually result in a coupled and nonlinear saddle point problem, for which numerical difficulties increase as the mesh size decreases.Let us consider a domain Ω ⊂ R d (d = 2 or 3), consisting of a fluid region Ω f and a porous media region Ω p separated by an interface Γ. As shown in Fig. 1.1, Ω = Ω f Ω p and Γ = Ω f Ω p . The interface Γ is assumed to be smooth enough [23].The fluid flow in Ω f is governed by the steady state Navier-Stokes equations: