Drilling mud is an important part of drilling engineering. It plays a key role in ensuring safety， quality and rapid drilling， and is called “the blood for drilling”. As the hole depth gradually deepens， the existing drilling mud is unable to meet the requirements of current core drilling due to high density， poor rheological property， and thick mud cake. At present， low solid mud is mainly used， while various chemical treatment agents are added to improve its performance. This paper introduces the application of low solid phase drilling mud with X-A film-forming agent in drilling in LaoXuZhai copper mine.