The stratum was hard and compact with weak abrasiveness, stuctural development, easily inclining and complex lithology in Beijing Fengjiayu iron mine. The inclination angle change range was large (-55～60 ) in tunnel horizontal drilling; during upward hole construction, the flushing fluid was easy to outflow down along the drill pipe, which caused great harm to constructor and drilling equipment. The hidden dangers in the tunnel brought difficulities to drilling construction. Therefore, some measures were chosen to ensure construction quality and safety, such as selecting Z7559 full hydraulic drilling machine with light-weight main body and small installation space, full-packed assembly, custom-made soft matrix diamond bit, rational selection and adjustment of flushing fluid properties and pump volume, proper adjusting drilling parameters, restricting roundtrip meterage and reasonable installation of drilling machine.