The paper introduced the construction technology of well drilling and cementing for large diameter drainage hole in Wutongzhuang coalmine. The designed depth is 646m, the termination diameter is 520mm and the tolerance of hole bottom coordinate should not be more than 5m. 646m case (426mm in diameter and weighted more than 90t) was put down to the borehole with cementing. Because of large borehole diameter and high demand of verticality, construction was difficult. Safely putting down φ426mm case and cementing were the key points to prevent hole deviation. Based on the effective deviation control and casing measures, the construction was fulfilled by small diameter pilot hole drilling and borehole reaming with rational drilling tool assembly and drilling mud.