Abstract: The irregular distribution of residual coal pillars between district main roadways and the working face leads to problems such as crossing coal passes, old roadways, and thin coal zones during mining. To achieve precise and thorough extraction, it is necessary to optimize the layout and rationally mine the residual resources. Focusing on the first isolated working face in Yuecheng Coal Mine, this study investigates the reasonable size of narrow coal pillars for roadway protection and surrounding rock control by using theoretical calculations, numerical simulation (FLAC^3D), and field monitoring. By theoretical calculations combining the Bieniawski rock mass strength criterion with empirical formulas, the reasonable size range of the coal pillars is preliminarily determined. By establishing numerical models with different pillar widths for different sections, the stress distribution, plastic zone evolution, and surrounding rock displacement patterns were analyzed. The reasonable pillar width was finally determined as 8 m for Model 1, 7～8 m for Model 2, and 15 m for Model 3. The maximum stress is concentrated 6～8 m from the working face and remains at a high level within 10～20 m; accordingly, the advance support distance is set at 20 m. Field application shows that the selected pillar sizes effectively control surrounding rock deformation, providing a technical reference for narrow pillar roadway protection in isolated working faces under similar geological conditions.