Chinese fir (Cunninghamia lanceolata (Lamb) Hook.) in the Dagangshan region of Jiangxi Province in southern China was selected to explore the impact of climatic factors on tree ring width growth. Results showed that the signal-to-noise ratio (SNR) and mean sensitivity (MS) were large while the first order autocorrelation coefficient (FOAC) was small, and the chronology contains abundant climatic information. The tree ring width index of Chinese fir was significantly positively correlated with the precipitation in December of the previous year and June of the current year, and significantly negatively correlated with that in the current May and August. The tree ring width index was significantly positively correlated with the temperature in April and May of the current year, but significantly negatively correlated with that in July of the current year. The tree ring width index had a good change consistency with the warmth index (W_i) and humidity index (H_i). The response function of Chinese fir ring width analysis shows that the warmth index is the main factor affecting tree ring growth, followed by the humidity index, mean annual precipitation, and mean annual temperature. The comprehensive effect of temperature and precipitation factors have significant influence on the tree ring width growth of Chinese fir. Results can provide a scientific basis for studying the effect of climatic factors on tree growth in sub-tropical regions in China and many other parts of the world.