The stability characteristics of methanol flow boiling over a nonuniformly heated surface has been investigated. An axial heat Aux distribution corresponding to a neutral stability condition, at which nucleate and film boiling can coexist steadily, was identified under various system pressures, liquid subcooling and liquid flowrates. An increase (decrease) in the bottom heat flux under nucleate boiling mode would enhance (weaken) the relative stability of the film boiling mode. Furthermore, nucleate boiling would become more stable under increasing liquid subcooling. The dependence on system pressure is relatively weak. The ＇equilibrium heat flux＇ is proven for the first time, to exist on an indirectly conductive heating surface, which can serve for direct comparison between stability characteristics among different boiling systems.