Brain trauma is one of the main diseases that threaten human life. The modality of severe brain trauma reaches a level to 30-50%. The damage is even higher because brain trauma often occurs in young men. Highway accident and gun trauma resulted in high brain trauma in western countries, as well as in Chinese. Through decades of hard work, the modality of severe trauma decreased significantly, but the damage of neuron structure and function was still hard to recur. According to the degree, nerve function and psychia abnormal will occur at patients, especially in those with mild to moderate trauma. They are called post brain trauma syndrome which will last days to years, affecting human work and study, while drug therapy has little effects. ILLLI was a new technology originally used in former Soviet Union. With its simple structure, convenient manipulation and low price, ILLLI was used clinically in former Soviet Union and China . Laser is transported through quartz fiber. Intravascular irradiation is carried out at superficial big veins, irradiating the blood circulation directly. Extra irradiation is carried out at the rich capillaries at mouth cavity. Parameters: power output: 3-5mw; irradiation time: 30-60mm. This method is developed rapidly in China, used widely in brain and heart vascular diseases, deafness, thrombotic vascularitis, chronic bronchitis, psoriosis. It is reported that laser irradiation can improve the symptoms resulted from brain trauma, such as headache, dizziness, amnesia, paralysis . Nevertheless, the mechanism is studied little, and the systematic experimental-control study of the treatment of brain trauma is even less. In this study, brain trauma model rat was irradiated at the humeral vein by low level diode laser in vitro. The reaction of rat memory and brain free radical was observed and the significance and mechanism were discussed.