We collected 20-year-old Larix principis-rupprechtii from a plantation in Qinling to explore the contents of C, N and P and their ecological stoichiometry characteristics in fine roots, stems and needles in different seasons. The content of C increased first, then decreased and increased again throughout the growing season (May to October). The order of the mean content of C in organs was stems > needles > fine roots. The content of N in fine roots, stems and needles tended to fluctuate during the growing season. The content of P in both needles and fine roots decreased first, then increased and decreased again, then remained stable. The content of P in stems decreased first and then increased, then decreased gradually. The order of the mean content of both N and P in organs was needles > fine roots > stems. The content of N had the greatest variability in fine roots and needles throughout the growing season. The coefficient of variation (cv%) of P was greatest for stems. The variability of C in the 3 organs was the smallest. The changes in C:N and C:P ratios were opposite to that of corresponding N, P content in fine roots, stems and needles. The ratio of N:P peaked in stems and was minimal in fine roots. The order of the cv% for C:N throughout the growing season was fine roots < stems < needles and for both C:P and N:P was fine roots < needles < stems. Factorial analysis of variation for each parameter, with sampling season and organs as independent variables, showed that the content of C, N and P and C:N mass ratio mainly depended on the organ. C:P and N:P mass ratios were mainly determined by the interaction of organs and season. The mass ratio of C:N:P was similar in fine roots (369:7:1) and needles (309:10:1). The characteristics of C, N and P stoichiometry were relatively stable in fine roots. Quantitative characteristics in fine roots were affected less in different seasons in L. principis-rupprechtii in Qinling, which helps in analysis of the ecological system.