Under the background of climate change, droughts have occurred widely and frequently in North China in recent years. Using tree-ring to study droughts has advantages such as accurate dating, strong continuity and high resolution. This paper uses the Chinese pine ring-width of Xiaowutai Mountain, China, to analyze the correlations between the ring-width and climatic factors. The results show that the standard and residual chronologies of Chinese pine have significant correlations between spring precipitation, 0 cm ground temperature in May, average relative humidity of April and May, hours of sunshine and percentage of sunshine in May, and Z index of spring. The Chinese pine ring-width is fundamentally affected by the precipitation of the study area. 0 cm ground temperature, average relative humidity and hours of sunshine all affect the ring-width by affecting the soil water content indirectly. The years when the Chinese pine ring-width index of Xiaowutai Mountain falls into 0–0.80 could indicate spring drought years. This paper has demonstrated the feasibility of applying tree-rings to study the spatial and temporal development of drought in the study area.