Objective To develop a precise method for analyzing urinary peptides based on electromembrane extraction(EME)combined with liquid chromatography-tandem mass spectrometry(LC-MS/MS),and to evaluate its potential applicability in tumor biomarker screening.Methods A total of 15 disease-associated peptides were selected as the target analytes.A supported liquid membrane(SLM)composed of n-octanol containing 5%di(2-ethylhexyl)phosphate was employed,with the donor phase being a 1∶1 mixture of urine and 100 mmol/L formic acid and urine,and the acceptor phase being 20 mmol/L formic acid containing 50%dimethyl sulfoxide(DMSO).After EME at 40 V for 15 min,the acceptor phase solution was analyzed by LC-MS/MS.Subsequently,the method,EME combined with LC-MS/MS(EME-LC-MS/MS),was preliminarily validated utilizing urine samples from 12 healthy controls and 7 patients with urinary system tumors.Results All 15 peptides exhibited excellent linearity in the range of 0.1-100.0 ng/mL(r≥0.995),with the limits of detection(LODs)being 0.01-0.50 ng/mL and the limits of quantification(LOQs)being 0.03-1.50 ng/mL.The spiked recoveries ranged from 21.0%to 71.2%,with relative standard deviations(RSDs)of 0.8%-20.0%(n=3).Small-sample analysis of clinical specimens revealed that the concentration of bradykinin 1-5 in the urine were significantly higher in tumor patients(median:0.65 ng/mL)than that in healthy controls(median:0.37 ng/mL)(P<0.05),suggesting its potential as a specific biomarker for urinary system tumors.Conclusion The EME-LC-MS/MS method established in the study features simplicity,high efficiency,and high sensitivity,enabling precise determination of trace-level peptides in urine samples.Moreover,this approach provides a reliable methodological basis for disease biomarker screening and promotes the clinical application of electromembrane extraction.