The P. heterophylla and its adulterants were identified by HPLC-CAD fingerprint of sucrose and oligosaccharides in P. heterophylla. The improved quantitative analysis of multi-components with a single marker (iQAMS) was further established for simultaneous determinations of sucrose and oligosaccharides in P. heterophylla. The HPLC-CAD fingerprint and similarity coefficients between P. heterophylla and its adulterants showed significant differences. The relative errors (REs) between iQAMS method and external standard method (ESM) were below 3.00%, but significant difference was shown between iQAMS (different marker for whole program with gradient elution) and QAMS (one marker for whole program with gradient elution), indicating that QAMS method should be improved, especially for gradient elution which influence the response of analytes. The accuracy, precision, reproducibility, and stability of this method were validated which exhibited satisfactory results, indicating that iQAMS method could be used for quantitative analysis of sucrose and oligosaccharides in P. heterophylla instead of ESM. The iQAMS combined with HPLC-CAD fingerprint could be used to determine the content of each oligosaccharide, and it can be used for quality control of P. heterophylla.