The diagnosis of bladder cancer (BC) is currently based on cystoscopy, which is invasive and expensive. Here, we described a non-invasive, low-cost BC diagnosis method based on a desorption, separation, and ionization mass spectrometry platform (DSI-MS) that adopts N, N- Dimethylethylenediamine (DMED) as a differential labeling reagent. The DSI-MS platform avoids the interferences from intra- and/or inter-samples, while the DMED increases detection sensitivity and distinguishes carboxyl, aldehyde, and ketone groups from untreated samples. Carbonyl metabolic fingerprints of urine from 28 BC patients and 38 controls were portrayed and significant differences of some potential biomarkers were observed. The mechanisms of the changes have been discussed. Logistic regression (LR) was applied to discriminate BC from controls and an accuracy of 87% was achieved. We believe this patient-friendly method provides a hopeful approach for BC rapid point-of-care diagnostic.