A spiral structure of cooling tower is designed for heat exchange of gas & liquid.The method includes the locating of the outer spiral line on the tower wall and the inner spiral line on the central axial pipe, as well as the topologic shape in the plane for the curving board between the two spiral lines. According to the basic parameters of cooling tower, the critic parameters of spiral curving board can be ascertainable, so as to accurately link up the tower board with the tower wall and the inner axial pipe.