Abstract:The growth pattern in stem diameter of five sample trees of Larix principis-rupprechtii was measured by using dendrometer from June to September in 2005 in the south of Liupan Mountain, Ningxia. The results indicated that in the days with daily rainfall＜10mm, the daily fluctuation of stem diameter presented a periodical cycle and it could be divided into three phases: shrinking phase, expansion phase and growth phase. However, daily fluctuation of stem diameter presented a different pattern at in the days with daily rainfall≥10mm and followed clear days. Based on the method defined by Deslauriers et al. for estimating daily growth of stem diameter, a modified method was presented to calculate daily and cumulative growth of stem diameter, and the results showed that seasonal pattern of daily growth were similar among five sample trees. During June and July period, stem grows quickly with an average growth rate in stem diameter at 27.0-44.2μm per day. Relatively, It grows slowly during August and September period, with a mean growth rate at 10 μm per day. Both daily and cumulative stem growth were significantly different among sample trees, which could attributed to the difference in tree domain and their positions in the stand. The pattern of cumulative growth could be fitted by the power function satisfactorily. Principle Component Analysis and Partial Correlation Analysis indicated that the meteorological factors could be classified into three groups, and daily precipitation, minimum daily temperature, average daily solar radiation and average daily vapor pressure deficit were four significant factors to determine daily stem growth.