In our previous work,we identified ∼100,000 metal-poor stars ([Fe/H] < −1.0) from the LAMOST Survey. This work estimates their chemical abundances and explores the origin and evolution of the Galactic metal-poor disk. Our chemo-dynamical analysis reveals four main populations within the metal-poor disk: (1) a primordial disk older than 12 Gyr with [Fe/H] > −1.5;(2) debris stars from the progenitor galaxy of Gaia–Sausage–Enceladus (GSE),but now residing in the Galactic disk;(3) the metal-poor tail of the metal-rich,high-α disk formed 10–12 Gyr ago,with metallicity lower limit extending to −2.0;(4) the metal-poor tail of the metal-rich, low-α disk younger than 8 Gyr, reaching a lower metallicity limit of −1.8. These results reveal the presence of a primordial disk and show that both high-α and low-α disks reach lower metallicities than previously thought. Analysis of merger debris reveals that Wukong, with extremely low metallicity, likely originates from merger events distinct from GSE. Additionally, three new substructures are identified: ShangGu-1, characterized by unusual [Fe/H]-eccentricity correlations; ShangGu-2,possibly heated disk stars;and ShangGu-3,which can be divided into four subgroups based on differing orbital directions,with two aligning with the previously known Nyx and Nyx-2.