Safety regulation is one of the important functions of modern government. Since the reform and opening up in 1978, in the process of promoting the construction of a regulatory state, the efforts of Chinese governments at all levels to strengthen safety regulation coexist with the safety regulation quality which is still relatively weak. How to understand the contradiction between the efforts of safety regulation and the weak safety regulation quality? This article constructs a scissors-gap model of regulate quality and risk level to describe the ongoing process of the scissors gap between the supply of safety regulation and the demand for risk governance in the process from routine regulation to campaign-style governance based on the evolution of risk and the adaptability of regulation. The framework regards risk as a dynamic evolution process of accumulation and superposition, and requires the establishment of a suitable dynamic regulatory behavior model. The traditional campaign-style regulation mode can temporarily control risks, but it cannot stably control or reduce risks to a lower level for a long time. There is a scissors gap between the dynamic evolution of risks and regulatory behavior, and various risks and hidden dangers continue to accumulate, which may eventually lead to major accidents when triggered by specific factors. Based on this analytical framework, this article conducted an in-depth case analysis of the "4.29" self-constructed building collapse accident in Changsha, Hunan Province. Using process-tracing methods, the dynamic change of the gap between regulation quality and risk level in the process from routine regulation to campaign-style regulation under the joint action of driving factors, and the process of scissors gap between safety regulation supply and risk management demand forms, have been addressed and verified.