Objective:To study the suitable concentration and the security of topical mitomycin C(MMC) in preventing postlaminectomy peridural adhesion by 7.0T Micro MRI. Methods:Laminectomies were performed at L1 in 30 rats. Cotton pads soaked either with 0.1 mg/ml(group B),0.3 mg/ml(group C),0.5 mg/ml(group D),0.7 mg/ml(group E) MMC,or saline(group A) were applied to the operative sites for five minutes. To determine the somatosensory evoked potential(SEP), the rats were killed 4 weeks after surgey. The specimens were prepared for determination of the degree of scar adhesion according to Rydell method and the area of the scar with MRI. Results:No obvious adhesion were found in group D and group E. Severe peridural adhesion were formed in the control group(group A). The area of the scar with Micro MRI in group D and E showed significant decrease. The SEP did not alter obviously. Conclusion:0.5 mg/ml MMC may be suitable concentration in preventing postlaminectomy peridural adhesion.