Objective To determine the trajectories of the myelin water faction of the corpus callosum of infants.Methods Continuous collection of 100 health 0-2 years old baby.Inclusion criteria are as follows:the birth mother with no complications during pregnancy, no drinking habits,without hypoxia brain injury occurs,and developing normally,conducted by the pediatric neurology doctors clinical evaluation no abnormal neurological signs,no systemic diseases involve the nervous system.Using GE 1.5T magnetic resonance imager, 8 channel head coil,T1WI,T2WI and sagittal T1WI were performed,and the whole brain SPGR and SSFP sequence were scanned. The region of interest(ROI)was placed in the genu of the corpus callosum(ROI1),the central region of the body(ROI2)and splenium of corpus callosum(ROI3).The volume of ROI was(100 ± 20)mm3,and the myelin water fraction was calculated.Results The trajectories curve equation of the myelin water faction of the genu,body and splenium of the corpus callosum are as follows respectively:genu y=0.068 1ln(x)-0.330 6,R2=0.955 8;body y=0.062 8ln(x)-0.297 5,R2=0.937 3;splenium y=0.057 5ln(x)-0.265 2,R2=0.923 4.Conclusion The application of magnetic resonance myelin water fraction can be used to quantitatively evaluate the myelin development process.