Abstract: In the air reverse circulation drilling system，there is a positioning device also called correcting block between the inner tube and the outer tube of the double wall.The current correcting rectangular block usually lead to greater loss on the circulatory system pressure，so the structure of correcting block is optimized with the help of computational fluid dynamics.Researches on block structure of double-wall drill annular gap are carried out，and the square，triangle，trapezoid，and hexagon correcting block are designed.Using pressure changes as the evaluation criteria，the numerical simulation on pressure field of correcting block is made with computational fluid dynamics software.Finally，the hexagonal correcting block is chosen.Then the three-dimensional numerical simulation on the pressure field of hexagonal block is made.It is further verified that hexagonal blocks can reduce the local pressure loss.Compared to the characters of other several correcting blocks，it owns a superior structure.

Key words: Computational fluid dynamics, Correcting block, Structural optimization