Fiberglass preforms or fabrics are the main structural form for making glass fiber reinforced plastics (abbreviated to FRPs). Once the fiber and matrix properties as well as fiber volume content are fixed, the mechanical properties of the FRP products are predominantly dependent on the structural parameters of the fabrics, i.e., fiber arrangement angles and areal weights. It is a difficult task to experimentally determine those parameters. Not only does high expenditure both in time and in money have to be spent, but also it is hardly possible to obtain an optimized design only through the trialand-error tests. This paper describes how to design the two structural parameters of any multiaxial fabric only based on the mechanical properties of the fiber and matrix materials. The load shared by any layer of the FRP is determined through the classical laminate theory, whereas the homogenized stresses in the fiber and matrix of this layer are calculated using micromechanics Bridging Model. The homogenized quantities are then converted into true stresses before compared with the fiber and matrix strength data to assess whether or not the layer is failed. If there is a fiber failure, or there is a matrix failure together with a maximum strain of the laminate which is greater than a critical value, the corresponding load applied on the FRP is defined as its ultimate strength. All of the design formulae involved are explicit and analytical, and the designed performances of the resulting FRPs agree well with the experimental counterparts. The present work provides an efficient methodology for engineering applications.