Hot dry rock (HDR) is a renewable green clean energy source; however its exploration and development is characterized with great burial depth, broken strata, abnormal pressure, high temperature gradient, high temperature at the bottom of the hole (usually＞200℃), and there are many problems during drilling, such as circulation loss, unstable wellbore, falling stones, pipe sticking. This paper analyzes the key technical difficulties on high temperature drilling fluids: temperature resistance of agents and systems, foaming, circulation loss, wellbore stability etc. At the same time, with introduction of the development and Application of high temperature drilling fluids in domestic and foreign countries, research is conducted on the development trend of the high temperature drilling fluids so as to provide effective technical support to promote the exploration and development of dryhot rock resources in China.