Abstract: The study mentioned by the title was conducted to investigate the quality differences of samples of Polygonum cuspidatum leaves collected from different harvesting periods. After drying and crushing 16 batches of samples collected from March to October, an aliquot (0.1 g) was taken, and 5 mL of 80% (volume fraction) methanol solution was added. The mixture was ultrasonicated for 45 min, and centrifuged for 10 min. The supernatant was taken, and passed through a 0.22 μm filter membrane. The filtrate was analyzed by high performance liquid chromatography (HPLC). Gradient elution separation was performed on Agilent HC-C₁₈(2) column with a mixture of acetonitrile and 0.1% (volume fraction) phosphoric acid solution at different volume ratios as the mobile phase. Chromatograms of 16 batches of samples were collected and imported into a similarity evaluation system for similarity analysis. Using common component peak areas as variables, chemical pattern recognition methods such as principal component analysis (PCA), systematic clustering analysis, and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to distinguish samples from different harvesting periods. The 9 common components identified were quantified by the external standard method, and the seasonal variation patterns of the content of these 9 components were analyzed. It was shown that there were 17 common components in 16 batches of samples, and the similarity of the samples collected in March was less than 0.800, The 16 batches of samples were divided into 3 categories by systematic clustering analysis, which was consistent with the PCA classification result. The 5 potential quality difference biomarkers were screened by OPLS-DA, to distinguish the quality differences of samples from different harvesting periods. The content of components such as rutin, quercetin, and polydatin in samples from different harvesting periods varied with the seasons, with the content of styrene, and anthraquinone compounds highest in spring, flavonoids highest in autumn (quercetin content reached its peak in July), and phenolic compounds changing relatively steadily, which could provide theoretical basis for quality control of Polygonum cuspidatum leaves and determination of harvesting period.