For long time was textile production based on the traditional trial-and-error method. A lot of design systems now are oriented to the final appearance i.e. to the 2D or 3D yarn visualization or on the simulation of partial yarn properties without connections with fibers parameters and production technology. The main aim of this work is presentation of complex system for prediction of geometrical and mechanical - physical properties in line “fiber – yarn”. The design system allows: a) Specification of main fiber properties, b) Selection of proper technology, c) Prediction of yarn quality and properties (unevenness, appearance, strength etc.) The system also includes the properties of yarns produced on a new developed spinning system named as Novaspin (Cotton Research Institute VÚB Ústí nad Orlicí – CZ). The fiber – yarn” system is core of new original design software “ Libtex.