Understanding the contents and stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) is vital to evaluate the function and processes of a forest ecosystem. Overall, 18 sites in Shennongjia Forest from an altitude from 800 to 3000 m were selected to collect litterfall, humus, and soil (0–20 and 20–40 cm) samples in May, August, and December. The spatio-temporal distribution of C, N, and P contents and their stoichiometry were quantified, and the underlying driving factors were analyzed. Results revealed total organic carbon (TOC) and total nitrogen (TN) contents decreased from the topsoil to the deeper soil, while total phosphorus (TP) contents in the soil changed slightly with depth. Controlled by various sources and decomposition degrees, the ratios of C:P, C:N, and N:P decreased from litterfall to humus, further increased in topsoil, and decreased again in deeper soil. Considering the average values of all sites, only TN in litterfall and humus dissolved organic carbon (DOC) in soil, and C:N in litterfall exhibited a significant seasonal variation. With increasing altitude, the contents of TOC, TN, and TP significantly increased in soil, particularly in August, but fluctuated in litterfall and humus. This positive relationship in soil was remarkable for TOC and TN compared with TP. Pearson’s correlation and redundancy analysis indicated driving factors exhibited a more noticeable influence on the contents of TOC, TN, and TP in soil than those in litterfall and humus. Moisture content, vegetation pattern, bulk density, total Mn (tMn), total Fe (tFe), and clay content observably influenced the contents of TOC, TN, and TP in the soil, and thus affected its stoichiometry. This investigation provided a comparable dataset on the contents of C, N, and P and their patterns of stoichiometry, which are helpful to optimize forest management and ecosystems.