Objective To establish a rapid determination method for vitamin A, D₃, and E content in cereal-based complementary foods for infants and young children by online solid phase extraction-two-dimensional liquid chromatography simultaneously.Methods Sample saponification solution is purified by online solid-phase extraction. Then, vitamin A and E are separated and detected by the first-dimension chromatography, while vitamin D₃ is preliminarily separated in the first dimension and then transferred to the second-dimension chromatography for further separation and detection, with all quantification achieved by the external standard method.Results Vitamin A, D₃, and E exhibit a good linearity in the concentration ranges, with correlation coefficients (R²) being more than 0.999. The limits of quantification (LOQ) are 1.62, 0.308, and 13.9 μg/100 g for vitamins A, D₃, and E, respectively. The spike recoveries range from 92.4% to 109.2%, with relative standard deviations (RSD) between 0.36% and 3.08%. Additionally, the expanded uncertainties (k=2) for vitamin A, D₃, and E are 7.04%, 17.0%, and 5.30%, respectively.Conclusion With high simplicity, efficiency, accuracy, and reliability, this method enhances the automation degree in sample pretreatment, meeting the needs of batch detection of fat-soluble vitamins in cereal-based complementary foods for infants and young children.