中国北方现存六例建于《营造法式》刊行前（即1103年前）的七铺作斗栱实例，均为双杪双下昂，重栱偷心造，形式特征具有明显的相似性。七铺作斗栱历来被认为是高等级的重要建筑所采用的斗栱形式，极具研究价值。本文整理了现有测绘资料与研究成果，着重考察了各案例的三维激光扫描点云图像或摄影测量点云图像，以直观的方法探求各案之间的相似度。通过图像的对比分析结果从而与已有的研究成果或实测数据相印证，对于缺乏相关研究的案例通过图像的对比分析而带来启发，探析此六例七铺作斗栱在相似的形式之下，其几何设计方法与尺度规律的异同，以揭示其中的匠心和匠作的流传。

There are six examples that were built in northern China before the year 1103, when Yingzaofashi was published. They all share the same style of dougong - double xia'ang, seven Puzuo, four steps, which was considered to be of high value.This thesis collected previous surveying and drawings, and relative research, focused on the orthographic images of dougong, which were obtained through 3D scanning and photogrammetry, endeavoured to find the similarities or differences of the apparent style and the same or the different approaches to them. Through the comparison and overlapping of these images, the descending angle of xia’ang and the detailed joints of the six examples can be observed directly. Then through the dimensional analysis of the data, the geometric design of dougong could be concluded as the different patterns, which reflected the methodology of the design that done by ancient craftsmen.At the same time, this thesis also retrospected the previous methods of measuring and utilization of the 3D scanning points cloud, made suggestion to future work.