Abstract: Using the energy comparison method and comparison principle, we considered the global existence and blow up properties of the homogeneous Dirichlet problems in exterior domain of coupled nonlinear diffusion systems with reactions and convections, determined the critical Fujita curve and established the Fujitatype blow up theorem. The results show that the critical Fujita curve depends on the spacial dimension, convection and reaction terms of the systems.

Key words: asymptotic behavior, critical Fujita curve, reactionconvectiondiffusion systems