In order to investigate the physical and mechanical properties of the surface and prepare the basic tasks for creating physical models and etc., the geometric modeling of fabric structures for understanding their subsequent behavior is needed. Textile products are difficult to reconcile with the conventional and useful assumptions for analyzing the engineering structures. This is due to their discontinuities and non-isotropic properties. In the case of knitting fabrics, making a fabric model and using the force analysis method is very difficult, which is due to the three-dimensional structure of fabric. Hence it is necessary to consider assumptions about the conditions of the contact points between the yarns and the geometry of the yarn cross-section. Therefore the presence of large errors from the mechanical point of view in knitting fabrics will be certain. Determining the loop form is the key point in knitting. Dimensional properties of knitting are directly related to the shape of the loop. On the other hand, the determination of the loop shape and its dimensional properties for predicting the dimensional properties of the knitting fabric as well as its mechanical properties, such as tensile and pendulum behavior, is very important. Due to complexity of the knitting texture structure and presence of different assumptions, there are many reported theories that are not completely accurate, but they can be used for predicting fabric properties. In this research, using a Roller-Coaster loop model, a simulation was performed for a loop in a warp knitting structure, and by considering parameters such as loop’s height to width ratio and the yarn diameter, two distinct models were provided and through a software in a 3D environment, the loop model was simulated. In the following, by fabricating the standard fabrics of single bar and double bar warp knit, and measuring the dimensional parameters such as coarse density, row density, and the loop length, the matching rate of the proposed models were investigated. Also, the obtained results were compared with the validated models such as Allison, Groerg, and Raz, in which, the results were closer and more consistent with the presented models in this study.