Abstract: From the perspective of structure design of fitted suit and dress, this paper analyzes the properties difference between knitted fabrics and woven fabrics, as well as the influence on the aesthetic performance and fitness, then modifies the structure. In the experiment, conventional woven plain cloth and circular knitted sandwiched fabric are selected as garment fabrics, and their stiffness, draping performance, and stretch elasticity are tested. 165/88A size of suit and dress sample were made, the experiment compared and analyzed the size difference of horizontal dimension, longitudinal length and oblique parts, so as to explore the influence of different properties’ fabrics on the size of the upper part size. Results showed that: the shoulder position of the knitted suit is prone to deformation, therefore, the acromion should be reduced 0-0.3 cm, and the shoulder width should be reduced 0-0.4 cm; for some knitted clothing with large vertical size, like dresses, when using fabrics with a weight of 288.03 g/m², the length of the tops and dress should be reduced 0-1 cm; the optimized size of each part of the model can be obtained based on elastic elongation of knitted fabrics in terms of horizontal, vertical and diagonal directions, which is namely that the size of the woven model multiplies the change rate of the size of each part.