| In this paper, we consider the Turing instability of two classes cross diffusion models with three species where α0, α1, α2, β2, γ,γ0,γ1,m1, m2, r, ∈ and di(i= 1,2,3,4) are positive constant, Ω is a bounded domain in Rn.Through the linear analysis, the unique positive equilibrium point E*(u1*, u2*,u3*) of (1) (or (2))corresponding ODE model and semilinear reaction diffusion model is stable under certain conditions. But under the same conditions, when the diffusion coefficient is sufficiently large, E*(u1*, u2* u3*) is unstable equilibrium point of (1) (or (2)), it means that the Turing instability occurs. |