Abstract: The Zimmi mining district in Sierra Leone, located within the West African Craton, is known for yielding yellow diamonds predominantly classified as type Ⅰb, transitional type ⅠaA—Ⅰb, and type Ⅰb—ⅠaA, which commonly contain abundant sulfide inclusions. In recent years, the origin and evolution of lattice defects such as N₂V⁰, NV⁰, and NV^-, as well as the retention mechanism of isolated nitrogen (C-defects) in type Ⅰb diamond series from this region, have attracted significant attention in the fields of geoscience and gemmology. In this study, the natural type Ⅰb diamond series samples from the Zimmi mining district were investigated using micro-Raman spectroscopy, micro-infrared spectroscopy, cathodoluminescence microscopy, and electron paramagnetic resonance spectroscopy. From the perspective of lattice defects and mineral spectroscopy, the genesis and evolution mechanisms of lattice defects and their coupling relationship with dislocation glide were researched. The results indicated that during crystallization, the natural type Ⅰb diamond series samples from the Zimmi mining district underwent fluid metasomatism, host magma emplacement, and subsequent tectonic deformation, resulting in diverse geometric dissolution patterns and multi-directional dislocation glide traces on the (111) crystal planes. As the aggregation of the isolated nitrogen increased from the crystal growth center toward the rim, the concentration of the C-defect decreased, while that of the A-defect increased correspondingly. The formation and evolution of the dislocation network, as well as the retention of isolated nitrogen, are evidently controlled by multiple episodes of rapid tectonic exhumation in the region. This led to dislocation glide, climb, multiplication, and reorganization along the 111 direction, accompanied by the formation of vacancy clusters and subgrain boundaries, ultimately producing a characteristic multi-dimensional dislocation network. Dislocation glide is identified as the key factor responsible for the formation of defects such as N₂V⁰, NV⁰, and NV^-. A positive correlation exists between the concentration of these defect centers and the intensity of dislocation glide, which also contributes significantly to the brownish-yellow to brown colouration of the type Ⅰb diamond series from Zimmi mining district. This study provides a scientific basis for understanding the retention of C-defects, the evolution mechanism of NV defect, and related detection methods in such diamonds.