The utility model relates to a fin that cracks turns back in boundary layer, including substrate and the miniature fin of domatic, the miniature fin of domatic sets up in pairs on the substrate, and is every to constituteing by the little rib of a weak point and a long little rib, and short little rib and long little rib are the perk of substrate homonymy and sensing the other side mutually, long little rib highly is greater than the perk height of short little rib in the ascending perk in perpendicular to substrate side, every to in the miniature fin of domatic, short little rib is located the fluid flow upper reaches, and long little rib is located the fluid flow low reaches. When the fluid from short little rib flows long little rib when, can be turnd back in the boundary layer, fluid speed is improved with temperature gradient's degree in coordination, fluid perturbation increases, heat transfer performance improves, has reduced indirect heating equipment's volume, has reduced product cost.