Objective To develop a quantitative analysis of multi-components with single marker (QAMS) and validate its accuracy and feasibility for simultaneously determining 3-n-butylphthalide (b), sedenenolide (sen), and sedanolide (san) in celery seed extracts (CSE). Methods Three main effective components,3-n-butylphthalide, sedenenolide, and sedanolide,were selected as analytes for evaluating the quality of CSE. The relative correction factors (RCF, f) of 3-n-butylthalide to the other two thalides were calculated: f_b/sen=0.226, f_b/san =0.702. The external standard method was used to determine the title compounds in 6 batches of CSE and the results were compared with those of QAMS. Results The RSD of RCF calculated by different instruments was between 4.4%-6.7%. The RSD of RCF calculated by the same instrument with different chromatographic columns was between 2.3%-3.6%. The established RCF had a good reproducibility. The quantitative results of three thalides determined by external standard method and QAMS method were not significantly different. Conclusion The present method can serve as a new mode to determine multi-components in CSE when standard substances are unavailable.