The characteristics and variations in micro-climate across alpine regions play an important role in tree-line prediction and the climate-growth relationship. Due to a lack of meteorological stations, there is little knowledge about dynamics of soil temperature (ST) and water content (SWC) during freeze-thaw cycles in sub-alpine regions, especially in north-central China. In present study, based on in situ measurements from 2012 to 2016, seasonal changes in ST and SWC at the upper and lower limits for coniferous forest were analysed and compared on Luya Mountain, China. The results showed that (1) soil at treeline thawed in early May and froze in late October on the northern slope, and soil on the southern slope lagged behind about a week. Growing season length and mean STs of growing season have no significant differences between the northern and southern slopes (122d, 8.1℃ and 110 d, 7.6℃, respectively). (2) The lowest SWCs for the northern and southern slopes were in January, and the highest were in September and October. And, in growing season, SWC of treeline at the southern slope was significantly greater than that at the northern slope (0.350m³/m³, 0.247m³/m³). (3) The thermal indices for the soil across the treelines were smaller than the values at low elevation (2040 m), whereas SWC during the growing season was significantly greater. These results revealed the coupling relationship between ST and SWC during soil freezing and thawing in sub-alpine areas, and confirmed that the radial growth of conifer trees at low-elevation on Luya Mountain was affected by soil drought, whereas the growth of high-elevation trees was limited by low temperature.