Stephania epigaea Lo is an important herbal medicine used as antiphlogistic and analgesic drugs. Its major components are dicentrine (1) and sinomenine (2). In the present study, a rapid, accurate, and precise method for simultaneous quantitation of dicentrine (1) and sinomenine (2) in S. epigeae using 1H NMR spectra was developed. The deuterated solvent of DMSO-d6 enabled satisfactory separation of the signals to be integrated in 1H NMR spectrum and dimethyl terephthalate was selected as an internal standard. The feature signals of δ 7.57 and 5.70 were selected for quantifying the dicentrine (1) and sinomenine (2), respectively. Validation of the quantitative method was performed in terms of specificity, accuracy, precision, and stability. This work implied that quantitative 1H NMR represents a feasible alternative to high-performance liquid chromatography-based methods for quantitation of dicentrine (1) and sinomenine (2) in S. epigeae and is suitable for the quality control of S. epigeae.