This study explored the phase synchronization in young, old adults, and old cognitively declined adults using 2 minutes baseline resting EEG data. Sixteen young students recruited from shanghai university and eighteen elders recruited from a community in Shanghai, including nine old adults and nine old cognitively declined adults, participated in our experiment. The global phase synchrony index was calculated in each 1 second epoch and averaged for all EEG frequency band (delta, theta, alpha1, alpha2, beta, gamma1, gamma2). Then, we analyzed global phase synchronization, fronto-parietal functional coupling and frontal functional coupling at alpha2 band for three groups. The results revealed that old declined adults had decreased global phase synchronization at theta and alpha2 bands and lower frontal and fronto-parietal functional coupling at alpha2 band than old controls. Relative to young adults, the old controls had an active mechanism of compensation to maintain normal cognitive performance. In conclude the frontal and fronto-parietal functional coupling in alpha band may be helpful markers of cognitive decline associated with aging.