Abstract: In the design of seamless knitted garments, experiential methods are usually adopted, it is both time consuming and tedious. On the basis of testing the fabric structure parameters and finished size of seamless knitted garments, this paper investigated the influence of some important factors including fibre sort, surface density and fabric texture on seamless knitted fabric structure and finished size at first. It was found that on normal manufacture conditions, finished products’ fabric structures are decided by the materials sorts and surface density. The fabric structure and machine gauge determine the garment size. Then the quantificational relationship between finished garment size and these factors such as materials sorts, surface density, fabric structure, machine gauge was studied. Finally, a new prediction method for seamless knitted fabric structure and finished size was established. Using this new method, knitted fabric structure parameters and seamless garment’s size can be predicted by material sort, surface density, machine gauge and fabric texture.