Abstract： Objective To study the effect of borneol on myelin of the central and peripheral nervous systems. Methods The rats were divided randomly into low-dose borneol treatment group (10 mL/kg,n=18) and high-dose borneol treatment group (13 mL/kg, n=18). Controls (n=18) were chosen and treated with 10 mL/kg paroline. Rats were sacrificed 24, 48 and 72 h after the treatment, and the blood, brain and sciatic nerves of these rats were prepared, respectively; the level of serum myelin basic protein (MBP) was detected and the morphological structure of myelin was observed with transmission electron microscope. Results The content of serum MBP in the 2 treatment groups was advanced markedly as compared with that in the control group 24, 48 and 72 h after the treatment (P<0.05);however, no significant difference was noted between the 2 treatment groups (P>0.05). The content of serum MBP was the highest 24 h after the treatment, gradually decreased following the prolongation of time; significant difference was noted between each 2 time points (P<0.05). Transmission electron microscope indicated abnormality in myelin of the central nerves at all time points, showing inordinate shape, rupture between layers and tangle among fibers; the abnormality was the most obvious 24 h after the treatment, gradually abatement following the prolongation of time; decreased myelin in the sciatic nerves was showed only at 24 h after the treatment, while normal at other time points. Conclusion A certain degree of abnormality of myelin of the central and peripheral nervous systems in rats can be caused by borneol.