The formation encountered in drilling the potassium geological scientific drilling borehole LDK02 in deep Lop Nur Salt Lake was mainly the Quaternary loose overburden, where bit burial was prone to happen due to borehole collapse in gravel, and bit sticking due to borehole contraction in clay, resulting in the hole wall extremely unstable and accidents easy to occur during drilling. Brine used to prepare the drilling fluid on-site had a significant influence on the performance of the additives of the drilling fluid, resulting in many problems of the drilling fluid, such as poor colloidal stability, easy sedimentation and delamination, ineffectively carrying and removing cuttings. To deal with the above problems, the ionic composition analysis was carried out on the on-site brine, and the additives with good salt resistance was selected to make brine based drilling fluid, which was applied in drilling the borehole LDK02 with good results, ensuring the smooth implementation of the drilling work.