The feasibility of the near infrared diffusion spectrum of local cortex for study of effect of anhydration solution is analyzed. 60 SD rats were divided in random into three groups A, B, C, which are treated by 0.9% NaCl, 20% mannitol and 7.5% NaCl through vena cava respectively. The near infrared diffusion spectrum of local cortex were collected continuously before and after the injection by a bifurcated fiber probe invivo in a mini-invasive way. Then the changing rules of the spectrum were analyzed. Few changes of the spectrum were observed in the group A(0.9% NaCl), while, relative changes of the absolute value of the spectrum slope between near infrared range increased by (5.5±1.2)% for group B (20% mannitol) and (10.5±2.5)% for group C (7.5% NaCl). The differences among three groups make statistic sense (p<0.05). The near infrared diffusion spectrum of local cortex can be used as a new method for estimation of effect of anhydration solution.