In the Xiaoxing' an mountain of northeastern China, the primary temperate forest is dominated by Korean pine (Pinus koraiensis Sieb. Et Zucc) mixed with some deciduous species. Furthermore, Korean pine is a major source of timber production in this area. In spite of the importance of this tree species, no published data are available on the daily stem radial variation of Pinus koraiensis and its response to meteorological parameters in northeastern China. In this study, we measured the growth patterns of stem diameter of Pinus koraiensis between April and November 2012, in Liangshui National Nature Reserve. Automatic point dendrometers were used for the continuous monitoring of tree growth. To perform the statistical analyses, the data were split into 15-day intervals during the growing season. The relationships between stem radial increment rate and meteorological parameters were assessed using the Pearson correlation coefficient. The meteorological parameters measured were mean, maximum and minimum air temperatures, soil temperature, air relative humidity, vapor pressure deficit, and precipitation. By dividing the dendrometer day-night data, our results demonstrated that the diurnal growth pattern was resolved into the three distinct phases: (1) radius contraction phase, (2) radius expansion phase, and (3) radius increment phase. During the period of measurement, the diameter of the stem usually exhibited daytime shrinkage and night-time expansion. An entire circadian cycle was constituted of a phase of contraction followed by a phase of expansion, plus a phase of radius increment when present. The stem circadian cycle generally lasted about 24 h, but heavy rain could cause irregular cycles of more than 24 h, largely due to a longer expansion phase. The growth of stem diameter of Pinus koraiensis started in late May, and ended in late July. The largest stem growth rate was obtained in mid-June. The cumulative radical increment of Pinus koraiensis between April and November 2012 was 800 μm. There was a markedly difference in the growth of stem diameter of Pinus koraiensis between tree sample individuals. In addition, evidence form our study suggested that the Gompertz growth function provided a better fit during the growing season. And this Gompertz growth function could explain approximately 90% of the variance of stem increment. We separately used two kinds of extraction methods of stem radius variation to examine the relationships between stem growth and meteorological factors. For example, for the diurnal growth pattern described by the three previous phases, the meteorological parameters of each phase were compared with the stem radius increment using simple correlation and response function analysis. The contraction in the first phase was primarily influenced by relative humidity, soil temperature and atmospheric vapor pressure deficit. During the second phase, precipitation and maximum air temperature were the main factors which influenced the radial recovery of stem. In the period of increment, minimum air temperature and precipitation had a significant effect on the growth in stem diameter. Furthermore, we used the daily maximum approach to extract the maximum of all daily stem diameter variation data. The difference between two daily maximum was the daily variance of the stem. Through analyzing the relationships between daily variation of stem radial and daily meteorological factors, we concluded that there were significant relationships between daily radius variation and relative air humidity, soil temperature and precipitation. The multivariate regression model showed that the daily analysis method could explain only 34% of the stem radius variation. However, the separation of the circadian cycle into distinct phases allowed the extraction of the SRI and allowed precise summaries of the meteorological data, and this method could explain 58% of the stem radius variation. In conclusion, our results suggested that meteorological factors during periods of expansion and increment played an important role on the stem radial growth of Pinus koraiensis.