Abstract: Discontinuities play a key role in the strength and stability of rock mass. During site selection of a project, granite is considered to be the ground or wall rock because of its high strength and integrality. Drillholes are the direct data of the target depth and reveal the rock mass during investigation. In the paper, Dayawan granite at Shenzhen is used as an example can to examine about the distribution of discontinuities in granite. Tectonic and secondary discontinuities are examined along drillhole depth. First, the discontinuities along drillhole and in the ground surface are contrasted. The occurrence distribution is similar because the same tectonic effect at the same site area. Secondly, the distance between two adjacent discontinuities along drillholes are analyzed (for direct effect RQD of drill cores).The discontinuity spacing and its frequency have evident power function relationship which is relevant to the RQD value.