Tree rings serve as precise archives of the environmental conditions that influence tree growth. In this study, we collected tree-ring cores from Schrenk spruce (<em>Picea schrenkiana</em>) in the eastern Tianshan Mountains and developed a robust ring-width chronology. Growth-climate response analysis revealed that total precipitation from the previous July through the current June is the primary factor limiting radial growth in this species, a relationship that remained stable over the period 1961–2020. Based on this strong climatic signal, we reconstructed annual precipitation for the region from 1830 to 2020. The reconstruction explains 37.6 % of the variance in instrumental precipitation records, demonstrating its reliability as a proxy for past climate. The reconstructed series identified distinct dry periods (e.g., 1830–1839, 1863–1868, 1919–1921, 1944–1947, 1975–1979, and 1989–1992) and wet periods (e.g., 1844–1850, 1869–1882, 1886–1899, 1930–1942, 1966–1973, 1980–1988, 1996–2001, and 2004–2018). The validity of our reconstruction is further supported by its strong agreement with other precipitation and drought reconstructions from nearby regions. Moreover, comparison with the Climatic Research Unit (CRU) gridded dataset indicates that our reconstruction captures precipitation variability across a broad spatial domain. By extending the instrumental record, this long-term precipitation series significantly enhances our understanding of climatic variability and its spatiotemporal characteristics in the eastern Tianshan Mountains. Notably, the reconstruction reveals a general upward trend in annual precipitation since the 1990s, which may enhance growth and carbon sequestration potential of Schrenk spruce forests in the region.