We have investigated the self-breaking mechanism of atomic scale Au nanocontacts at room temperature in air. In the conductance traces, we frequently observed traces showing both a 1G(0) (2e(2)/h) and 3G(0) plateaux, or only a 2G(0) plateau in the conductance regime below 3G(0). The statistical analysis showed a negative correlation between the appearance of 1G(0) and 2G(0) peaks, and a positive correlation between 1G(0) and 3G(0) peaks. This conductance behavior suggested that the symmetric triple atomic rows changed into a symmetric single row, while the asymmetric double rows broke without changing into a symmetric single row. The regular self-breaking process can be explained by the breaking of the thermodynamically stable Au nanocontacts which were formed during the self-breaking of the contacts.