The analysis is made on the geological characteristics of hot dry rock which is a kind of clean and reusable energy and the technical difficulties that might be encountered in drilling construction, such as high temperature and large drilling depth. On this basis, the application of hydraulic hammer drilling technology in hot dry rock field is discussed. According to the present technical level and construction ability, hot dry rock drilling needs 2 steps; with the present technical performance index, hydraulic hammer has the basic conditions for the first step drilling of 3000-6000m in well depth at the temperature of 150-350 ℃. The solution to the key technology improvement is also put forward.