In ancient times, architectural design was seen as a critical task in building technologies. Specifically, form, dimension and structural design are of significant. These aspects are associated with each other and to be emerged as a whole. Designing plan dimension was deemed to be the core of design technology due to its close relationship with module system. Thus, its evolution as well as development process typically represents and reflects the spirits and contents of design technologies in ancient China. In China, the materials regarding ancient architectural technology include Yingzaofashi(營造法式) of Song Dynasty and Gongchengzuofazeli(工程做法則例) of Qing Dynasty. They show many aspects concerning materials, structure, scale system and building. In Yingzaofashi, although the length of objects are decided by 'cai(材)' and 'fen(分)', there are no regulations on length, width and height of a building. However, in the construction of ancient buildings, the above mentioned basic scales are very important in both design and construction. The present paper attempts to discuss the significance, namely, the design principles of length, with and height of ancient chinese architecture.