Rainfall was partitioned into three parts through the vegetable canopy: Throughfall, stemflow and interception. This process played a determining role in water balance for forest stands and in regulating processes of this mountainous region. In present study, the experiment was carried out in Pailugou watershed in Qilian Mountains, in the arid region of Northwest China. In a 96-year-old Picea crassifolia forest stand, throughfall, stemflow and canopy interception of 34 rain events were observed from May 1 to September 31, 2015. Meanwhile, the related meteorological factors, including air temperature (T), air relative humidity (Rh) and precipitation (P) were simultaneously monitored by an automatic meteorological station in the outside forest. Then, we analyzed the characteristics of rainfall canopy partitioning and their influence factors. The results showed that: (1)During the total observation period, the total throughfall, stemflow and interception of Picea crassifolia forest were 275.9, 1.8 and 90.0 mm, and accounted for 75.04%, 0.48% and 24.48% of the total atmospheric precipitation, respectively. Meanwhile, their ratios varied significantly under different rainfall grades. (2)The three parts of rainfall canopy partitioning were significantly correlated with rainfall, rainfall duration, maximum rainfall intensity in 10 minutes and relative air humidity. With the increase of rainfall and rainfall duration, throughfall and stemflow would constantly increase and their ratios would become more and more stable. (3)The critical rainfall amounts for the occurrence of throughfall and stemflow were 0.8 mm and 9.6 mm respectively. Therefore, we concluded that meteorological factors were the important factors of rainfall canopy partitioning.