Abstract: During the operation of Paleogene strata in the eastern South China Sea, conventional drilling fluid systems cannot effectively plug hard and brittle fractured formations and permeable sandstone formations, unable to improve the pressure-bearing and anti-leakage ability of the formation, which has led to complex problems such as wall instability, stuck drilling, and lost circulation in many wells. This paper takes M block in the eastern South China Sea as an example, establishing a KL strong plugging drilling fluid system which showed excellent plugging performance when applied in the field, and effectively maintained the stability of the borehole wall. The successful application of the KL strong plugging drilling fluid system in Paleogene strata in M block can be used as reference for drilling fluids selection to improve the stability of the borehole.