Abstract: This paper delves into the ancient Chinese architectural system known as xiaomuzuo (non-structural carpentry), as documented in the “Yingzao Fashi”, focusing on the term furongban used in constructions like Buddhist and Taoist tents, zhuanlunjingzang (revolving sutra cabinet), and bizang (wall cabinet). Through an in-depth analysis of the xiaomuzuo system, this study uncovers a modular system within the Song xiaomuzuo, characterized by specific unit lengths of 1.2 chi and 0.66 chi. The deeper investigation reveals hidden modular units of 1.0 chi hidden in the tent of yajiao, along with 0.8 chi in the jiujixiaozhang (nine ridged small tent) and another 1.0 chi in the L-shaped plan formed bizhang (wall tent). These findings shed light on the intricate modular arrangements and stylistic coherence embedded in the design and construction of xiaomuzuo structures during the Song dynasty.