Increasing development in technology of manufacturing high-performance structures along with the importance of reduction in final products’ weight, have prompted textiles to be involved in designing such engineering technical materials. Knitted structures due to their high formability and complexity in designing, have allocated so specific position in technical application among the variety of textile products; however, improving their mechanical properties in terms of in-plane strength and high modulus is of the main requirement based on desirable end-uses. For improving mechanical properties of knit-based materials through their length and width directions, different techniques such as placing the reinforcing yarns into the structure could be effective in addition to increasing the fiber volume fraction as well. In this research accordingly, different weft-knitted structures were reinforced with warp and weft inlays in order to achieve biaxial weft knitted fabrics. Experimental investigation applied on these structures together with performing theoretical studies based on simulating analysis could provide better understanding upon their mechanical performances during different loading conditions as well as their formability into complex shapes. For this aim, such detailed structural models of these fabrics were developed according to meso and macro designing. In this study, biaxial knitted fabric including plain rib and interlock patterns, were produced on a modified modern flat knitting machine. Tensile tests in different directions were performed on biaxial fabric samples and their formability were evaluated. For predicting their mechanical properties, some structural equations contributed to the mechanical behaviors of biaxial weft-knitted patterns were extracted from the optimized geometrical models of fabric structures in meso-scale using Python programming environment and finite element software (Abaqus). Macro-scaled modeling is the second step in mechanical analyzing through which the fabric is considered as a shell structure. Instead of doing experimental tests on samples based on macro-scale modeling, it was decided to use multi-scale modeling for predicting the fabrics’ mechanical behavior. Comparing between the numerical simulation experimental results was applied in order to verify the proposed model. It was concluded that there is high correlation between the theoretical and experimental curves which suggests that both the macro-scale and multi scale geometrical models have high ability to predict the tensile behavior and formability of biaxial weft knitted fabrics. It is worthy to be stated that compared with the knitted fabrics, biaxial reinforced structures exhibit linear behavior in both course and wale directions, while subjected to tensile loadings. Also, the knit structure plays an important role to undergo the subjected tensile loading in bias direction and consequently its corresponding biaxial fabric exhibits non-linear behavior. During loadings, both weft and warp reinforcing inlays sustain higher fraction of the applied normal force. It was concluded that the higher frictional resistance formed between the constitutive yarns of the biaxial weft-knitted samples, plays an important role in their superior mechanical properties as compared with the conventional knitted fabrics. Keywords: biaxial knitted fabrics, geometric model, numerical simulation in meso, macro and multi-scale, tensile properties and formability.