Objective To establish a high performance liquidchromatography method for the determination of the content uniformity ofpromethazine hydrochloride, and to provide a reliable experimental basisfor the subsequent study of the content uniformity and content qualityof pediatric drugs after manual breaking tablets. Methods Highperformance liquid chromatography was used, octadecyl silane bondedsilica gel was used as the column filling agent, water (adjusted pH to2.3 with glacial acetic acid)-methanol (55 : 45) was used as the mobilephase, and the detection wavelength was ${254}\mathrm{\;{nm}}$ . ResultsPromethazine hydrochloride showed a good linear relationship in therange of 17.392~26.088 μg/mL, and the linear equation was: $\mathrm{Y}= {55272}\mathrm{X}+{348938}\left({{r}^{2}= {0.9986}}\right)$ . The method recoveryrate was between 100.22% and 101.40%, and the RSD was ${0.49}\%$ . The content uniformity ofpromethazine hydrochloride was in accordance with the provisions of thefour general principles of the Chinese Pharmacopoeia 2020 edition.Finally, this method was used to analyze the accuracy of children’sdrugs by different methods of dosing by the content and contentuniformity of promethazine hydrochloride tablets. Conclusion The method has strong specificity in determining the content uniformity and content of promethazine hydrochloride, and the accuracy and precision are good. The dose accuracy of children’s tablets is reduced by many times of dosing, and it also provides very important data theoretical and practical significance for promoting the dose accuracy of children’s tablets.