Abstract: Objective To select the best concentration, volume and checking time of Gd-DTPA dilution as an oral negative gastrointestinal contrast agent by in vitro/in vivo experiments. Methods (1) In vitro experiments :we used 0.05, 0.10, 0.15 and 0.20 m L intravenous injections of Gd-DTPA, which were diluted into concentrations of 0.25, 0.50, 0.75, 1.00 mmol/L, then we examined and made a contrastive analysis about the signal intensity and attenuation rate of 2 D-MRCP with different concentration contrast agent. (2) In vivo experiments: we used the optimum concentration of Gd-DTPA dilution with 50 and 100 m L, made 2 D-MRCP scanning on 20 cases in two groups in 4-6 minutes and 9-11 minutes respectively after oral administration of Gd-DTPA dilution, and observed the restraint of the high signal liquid in stomach and duodenum, and whether the patients had adverse reactions. Results (1) It showed that the high signal liquid in stomach and duodenum of some patients with oral administration of 100 ml dilution with 1.00 mmol/L concentration could be fully restrained in 9-11 minutes. (2) The allocation of oral Gd-DTPA dilution is simple, the effect of restraining the high signal liquid in stomach and duodenum is well after oral administration of little dilution, and the patients have no adverse reactions, so it is a good oral gastrointestinal contrast agent.Conclusions 2 D-MRCP scanning in suitable time after oral administration of Gd-DTPA dilution with proper concentration and volume can effectively restrain the high signal liquid in stomach and duodenum.