Exploring the causes of the concave curved form of the roofs in traditional Chinese architecture is key to understanding its unique esthetics and structural logic. Regarding its causes, the academic community offers various explanations, including esthetics and function, but research that delves deeply into specific construction techniques and material limitations and systematically explains how they lead to the precise roof forms is relatively insufficient, which limits our comprehensive understanding of the deep generative logic of this unique form. This study aimed to bridge this gap by systematically exploring the causes of the concave curved form of roofs in traditional Chinese architecture (such as flying eaves, upturned corners, and Ju zhe) from the perspective of construction technology. Through a systematic review of historical literature (especially Yingzao fashi (Treatise on Architectural Methods)); the empirical investigation and analysis of typical architectural examples; detailed research on the structural practices, material properties (especially the creep behavior of timber), and construction techniques of key timber components such as flying rafters, hip rafters, and rafters; and mechanical principles and computational simulation, this study found that the concave curved forms of different parts of the roof, such as the eaves (flying rafters), corners (corner upturn), and main body (Ju zhe), are not purely esthetic choices but are, to a large extent, technical responses or inevitable results stemming from objective construction constraints of the time, including limitations on timber length, component connection methods, structural load distribution, and long-term deformation. Based on these findings, this study proposes the concept of “Passive Form” to summarize this form-generation mechanism, emphasizing that architectural forms are not solely determined by subjective will but are rooted in the adaptation and transformation of real constraints in construction, providing a technical perspective rooted in practice for understanding the forms of Chinese traditional architecture.