Abstract: Spoon-billed Sandpiper (Calidris pygmaea) is a globally critically endangered bird, whose population dynamics have attracted significant attention and conservation research from ornithologists. Weitou Bay in Quanzhou is an important wintering and migratory stopover site for the species, yet no related studies have been reported so far. Therefore, the author conducted monthly monitoring surveys on Spoon-billed Sandpiper and associated bird species in Weitou Bay from May 2022 to April 2023. Results indicate that the southward autumn migration of Spoon-billed Sandpipers to Weitou Bay, Quanzhou, began in October, when some individuals settled for overwinter there. The wintering population size remained relatively stable at 5–6 individuals. The northward spring migration to Weitou Bay occurs from March to April of the following year, during which the population peaks, reaching a maximum count of 11 individuals. Two Spoon-billed Sandpipers with light green color bands (coded “7L” and “H0”, respectively) were identified. A total of 87 associated bird species, belonging to 12 orders and 28 families, were recorded in the whole year add up to 30 observations. Shorebirds dominated in both species diversity and abundance, including numerous rare and endangered species among them. Analysis of the annual population dynamics of the Spoon-billed Sandpiper and associated birds revealed a strong correlation between the wintering bird population and overall bird numbers in Weitou Bay. It is recommended to upgrade the surveyed areas inhabited by Spoon-billed Sandpiper and associated species to Nature Protection Area. Basic research on these birds should be enhanced to provide more scientific data for conservation efforts. Patrols, monitoring, and public awareness campaigns should be strengthened during the migration and wintering seasons of Spoon-billed Sandpiper and other wintering birds to reduce human disturbance. Furthermore, optimizing the aquaculture planning across the entire bay, continuing the removal of Spartina alterniflora (smooth cordgrass), reducing pollutant discharge into the sea, and improving the stability of the habitat structure in Weitou Bay are essential measures.