Abstract: In this paper three invariant theorems of interactive-structure between convection and diffusion for incompressible laminar shear flow and its ten inferences are presented. The invariance of interactive-structure means that the laminar shear flow and its linearized and nonlinear disturbance fields have the same interactive-structure between convection and diffusion and the same physical scales (including the time, spatial and velocity scales). In illustration of the present theoretical application, we deriv...