Since the 1990s，due to the superposition of multiple factors，such as the disintegration of the unit system，the downward shift of the focus of urban governance，the absence of special laws，and the path dependence under the bureaucratic system，the scope of performance and territorial responsibilities of sub district offices have been constantly expanding, and their legal and practical roles have also gone through a process from “coincidence” to “Deviation”. Although the role deviation of the sub district office has played a role of “filling the position” after the dissolution of the unit system in a certain historical time and space，from the perspective of the overall characteristics of the process of urban government, the “alienation” of the sub district office into a first-class government is not only the root cause of its performance dilemma，but also will further aggravate the “fragmentation” of urban governance and ultimately have a negative impact on the efficiency of urban governance. Therefore，adjusting the role of sub district offices in urban governance from three levels of clarifying understanding，optimizing responsibilities，and reengineering processes is a fundamental solution to the dilemma of sub district offices in performing their duties and to promote the optimization and reorganization of urban grass-roots governance system.