In the mid 1960s, the proven reserve was 93 million tons in Zhongguan iron mine area. Because of the deep groundwater table and difficult drainage, curtain grouting was adopted for water control to avoid high mining cost and protect the ecological environment. The curtain grouting has high demand of borehole verticality, hole deviation of the whole section should not be more than 2 m. Gyroscope directional deviation correction was explored in practice with success.