Based on the basic situation of the reform practice of “Public complaints have been processed without delay”，through the participation observation，in-depth interview and relevant statistical data collection of several streets and communities，this research report analyzes the positive effects of “Public complaints have been processed without delay” on promoting grass-roots governance transition，including enhancing the enthusiasm and standardization of grass-roots governance，strengthening the ties between cadres and masses，and greatly improving the people’s sense of gain and happiness. However，the investigation also found that under the pressure of response rate，resolution rate and satisfaction rate，some new problems occurred in grass-roots governance，such as the squeezing of grass-roots governance space，increasingly blurred governance boundaries，and new formalism reproduction. According to the research，the low cost of residents’ demands，the imbalance of powers and responsibilities at the grass-roots level，and the weak ability of conventional active governance are the main reasons for the problems. Then，some countermeasures and suggestions are put forward to deepen the reform of “Public complaints have been processed without delay” led by party building in grass-roots governance.