A case-based design technique is used in this study to analyze the structural form efficiency, unit scale, and statistical relationships among umbrella-shaped structure morphological parameters. The differences, characteristics, and applicable scales are compared between different umbrella structure types in terms of their morphological characteristics. The changes in structural form efficiency under material innovations and optimized structural morphologies are explained. The orders of different structure types and morphological characteristics under different parameters are given. Steel umbrella and reinforced concrete umbrella structures have more prominent unit sizes, while light steel umbrella structure and membrane umbrella structure are more prominent in terms of form efficiency. In addition to the better performance of the tubular type in terms of height (H), the segmented ribbed columnar type features the most prominent coverage area (S1) and structure form efficiency (α, β, and η). The correlation between different variables related to structural morphology is also revealed. By combining the limit value and range of related variables, and by establishing a function model of the relationships between structural form efficiency and size, this work provides a workable reference for umbrella structure unit design. Among them, H-ηhigh, S1-ηhigh, and S2-ηhigh explain the change trend of ηhigh with increases in H, S1, and S2. In the two sets of linear relations S2-Hhigh and S2–S1high, the approximate growth relationship between variables are given. If S2 increases by 1 m2, Hhigh can increase by 2.0 m, if S2 increases by 1 m2, S1high can increase by 83.6 m2. The Person correlation coefficients of the two sets of linear relations are 0.83 and 0.74, respectively, and the adjusted R2 values are 0.70 and 0.54, respectively. The practical application of the proposed technique for the conceptual design of umbrella structure building is also discussed.