Magnetic resonance structural images of 902 Chinese subjects were used to study the change of myelin content with the age based on the T1-weighted/T2-weighted ratio. Significant quadratic age effects were observed in white matter tracts and subcortical areas. The gender difference was reflected in the results that the myelin content levels are higher and begin to decline earlier in women. The inverted U-shape myelin-vs-age curve accords with the existing research literature. However, the age of the observed peaks may have been delayed by iron deposition in basal ganglia.