Objective To investigate whether the macromolecular materials could enter cerebrospinal fluid and brain tissues in craniotomy with incision or non-incision of dura and arachnoid. Methods Adult male SD rats were randomly divided into three groups according to the random number table. The dura and arachnoid of rats in group A were cut open during craniotomy after general anesthesia; epidural craniotomy was done in rats in group B after general anesthesia; rats in group C (control group) were only generally anesthetized. All the rats were injected with Evans blue, a tracer used to detect the results, half an hour before each time point (1,3, 6, 12, 24, 72 hours and 1 week) via vein. The rats were executed at each time point to obtain the specimens of brain. The content of Evans blue in brain tissue was measured by fluorescence spectrophotometer for statistical analysis. The water content in the brain tissue was measured in a part of rats selected in groups A and B preoperatively and at postoperative 3 and 27 hours. Results It was found that some regions of the brain tissue were stained light blue in group A at 1,3, 6 and 24 hours. The blue was much lighter in brain tissue obtained at 72 hours in group A, and no blue stained at 1 week in group A . The contents of Evans blue in the brain tissues of rats in group A at 1,3, 6, 12, 24, 72 hours and 1 week were (18.07±1.25) μg/ml, (36.21±0.78) μg/ml, (25.73±1.14) μg/ml, (16.53±0.84) μg/ml, (23.34±1.91) μg/ml, (43.34±2.25) μg/ml and (25.27±1.88)μg/ml respectively, which were significantly higher than (3.15±0.45)μg/ml, (3.36±0.33)μg/ml, (2.98±0.54)μg/ml, (3.47±0.55)μg/ml, (3.54±0.37) μg/ml, (2.88± 0.42) μg/ml and (2.85±0.22) μg/ml respectively in group B and (2.97±0.37)μg/ml in group C (P<0.01). There was no significant difference in water content in brain tissue before and after operation (P>0.05). Conclusion After craniotomy with incision of dura and arachnoid, some macromolecular materials can enter the subarachnoid space and the brain parenehyma through blood-brain barrier of the wound of the scalp if the dura is sutured loosely.