Entropy trajectories remain unclear for the aging process of human brain system. We employed the open data from an accelerated longitudinal cohort (PREVENT-AD) including 24 healthy aging participants followed by 4 years with 5 visits per participant to establish the brain entropy aging curves and distinguish with the age and cohort effects. This reveals that global cortical entropy decreased with aging while a significant cohort effect was detectable that people who were born earlier showed higher entropy. Such entropy reduction were also evident for most of the large-scale networks although with different speeds for different networks: the primary and intermediate networks reduce their entropy faster than the higher-order transmodal networks. We conclude two specific brain entropy features with aging: the shift of the complexity hierarchy of networks and the diversity of complexity increases among networks.