Abstract: County-level cities in southern Jiangsu Province are at the forefront of cultivating new quality productive forces and constructing a high-quality development environment within the county domain. This article takes ten county-level cities in southern Jiangsu as research objects. Based on practical analysis, it extracts the '3+3' high-quality development environment construction model featuring 'three highs and three optimizations', namely high-speed rail stations, university and research institutions, high-tech industrial parks, along with superior historical and cultural conditions, excellent natural ecology, and outstanding human resources as the driving force. The article further analyzes the correlation and logical connections between these factors and the development performance of new quality productive forces. Consequently, this article constructs an evaluation index system for the '3+3' high-quality development environment construction of county-level cities in southern Jiangsu. It evaluates and compares these cities, analyzes and confirms their correlation with the development performance of new quality productive forces, and compares their rankings with other related development evaluations. These analyses confirm the objectivity and effectiveness of the '3+3' high-quality development environment construction model of county-level cities in southern Jiangsu under the guidance of new quality productive forces. The '3+3' high-quality development environment construction model for county-level cities in southern Jiangsu, as revealed in this article, has certain reference value for understanding the development patterns of these cities. It also serves as a reference for other county-level units in promoting new quality productive forces and planning high-quality development paths. Furthermore, it can provide insights for promoting urbanization with county towns as important carriers in China.