The objectives of this research were to determine simultaneously the contents of two stilbene tetramers, carasinol B (1) and kobophenol A (2), and one stilbene trimer, (+)-α-viniferin (3), in the roots, tubers, and leaves of Caragana sinica in various seasons. A HPLC method has been developed for efficiently quantifying the three analytes in the plant. Using this method, different samples of Caragana sinica were evaluated. The results showed that the contents of 1, 2, and 3 in the roots were much higher than those in the tubers, and the contents of stilbene tetramers were maximal in winter while the contents of the stilbene trimer were maximal in summer. Compounds 1, 2, and 3 could not be detected in the flowers of Caragana sinica in our detection ranges.