Abstract: Against the backdrop of climate change and rapid urbanization, historic environments face mounting risks from both natural and human-induced hazards. Conventional "passive defense" conservation strategies are increasingly inadequate for addressing these multi-source challenges. Consequently, a proactive approach centered on "early detection and preventative intervention" is essential to enhance the safeguarding of historic environments. By synthesizing ancient Chinese urban planning wisdom with contemporary research on cultural heritage preservation, this study clarifies the concept of preventive conservation for historic environments. We categorize four key value elements—landscape base, street space, cluster lots, and characteristic nodes—and analyze the mechanisms of multi-source hazards. Recognizing the historic environment as a vulnerable receptor, we propose a preventive conservation framework rooted in value-based protection. Using the Ciqikou Historic and Cultural District in Chongqing as a case study, we explore flood response strategies, recommending a layered approach of "risk classification, element classification, and disaster stratification." This study aims to provide a methodological reference for advancing the preventive conservation of historic environments.