The development of new quality productive forces is the core driving force for the highquality development of county economies This article constructs an amended diamond model to establish an analytical framework for the dynamic mechanism of new quality productive forces in county economic development Taking the practice of developing new quality productive forces in Deqing County, Zhejiang Province as a case, it dissects the specific process of new quality productive forces development in county economies, extracts the effective mechanism for county economic development, and proposes corresponding policy suggestions The research shows that the development of new quality productive forces in county economies can be an iterative upgrading process consisting of five stages: singlepoint breakthrough, building a high ground, innovating a track, ecological cultivation, and external expansion The continuation and expansion of this process rely on the driving mechanism of four core elementsintegrating cultural concepts, strategic innovation, technological collaborative innovation, and crossregional industrial collaborationas well as two auxiliary elementsgovernment and opportunities This exploration not only can address the controversy over whether county economies can become a carrier of new quality productive forces, but also can effectively guide county economies to establish a systematic dynamic mechanism system for new quality productive forces development, breaking free from the constraints of the traditional “land + labor + resources” factordriven model