FEAs is particularly the major challenge that requires not only comprehensive knowledge on the intrinsic field emission mechanism of individual field emitter but also improvement on the actual proportion of field emitters that contribute to the FEAs. In addition to the screen effect, [11] thermal runaway is an important factor limiting the actual proportion of ZnO nanowire. [12] A general picture for the thermal runaway originated from the positive feedback of the self-heating characteristic of the Q1D field emitter on its thermal field emission current, which induces vacuum breakdown. Although several previous works have studied the thermal runaway mechanism for Q1D field emitter [13-15] and the melting of ZnO nanowire has been reported, suggesting the existence of thermal runaway, [12,16] the question of what temperature the individual Q1D ZnO field emitter can reach steadily, which determines the maximum emission current and breakdown field, remains unclear. With a high breakdown field, more emitters can be activated when increasing the applied field. One could also make better use of the ballasting effect usually existing in the ZnO nanowire field emitter itself [5] or equipped with an active driving device [17-18] and thus a highly uniform stable emission and a high emission current could be achieved. The field emission ring pattern was reported as a signature for the thermal field emission of the tungsten tip and the carbon nanotube (CNT). [19-21] It generally comprises the emission current from both the tip and the sidewall of the field emitter. Accordingly, one can obtain the thermal field emission current distribution along the emitter, which gives information on its temperature, by analyzing the ring pattern profile. [20] Compared to the field emission electron energy distribution that has been utilized to measure the temperature of individual CNT, [22] the method of field emission pattern is more simple. Furthermore, it can be applied in a large-scale substrate with potential application as a temperature monitor for FEAs. Although field emission ring patterns comprising several emission spots have been reported in ZnO nanowires, [23-24] they are different from those observed from the CNT, which is a continue ring. Their underlying mechanisms are due to the tip structure and the adsorbate instead of the thermal field emission. Considering that the ZnO nanowire The thermal runaway of a quasi-1D (Q1D) field emitter is an important cause of vacuum breakdown, which limits the field emission current density in field emitter arrays (FEAs). Comprehensive knowledge on the self-heating process of zinc oxide (ZnO) nanowires is important for obtaining a high breakdown field for activating more emitters. This work investigates the self-heating model of individual ZnO nanowire by considering the thermal field emission current distribution along the nanowire. Theoretical calculations suggest that the thermal field emission distribution along the nanowire can be reflected on the profile of the field emission pattern, ...