Near infrared spectroscopy(NIRs) technology was utilized for assessing effects in treating traumatic brain edema (TBE). Firstly, models for rats witht raumatic brain edema were copied according to Feeney’s apparatus. Then rats were given mannitol with different dosages(large and little) according to their groups. Simultaneously rat’s brain tissues were monitored in vivo and real time by NIRs mini invasive detector developed by theauthors’laboratory.And the water content of the brain tissues was measured by the wet and dry weight method at 1, 6, 24, 72 and 120 h after the injury and the treatment. Then, effects in treating TBE with different dosages were assessed by analyzing reduced scattering coefficient(μ′s) data measured by NIRs and brain water content(BWC) before and after injecting dehydration. Finally, the authorsfound that reduced scattering coefficient(μ′s) ofrat’slocal cortex is a good indicator of assessing effects of treatment of TBE and that may be a preferable approach to assessing effects in vivo and real time in treatment of brain injury.