Abstract: Owing to its architecture in which every yarn (fibre bundle) densely and spatially interweaves and contacts with each other, three dimensional and multidirectional braided composite is superior in many performances to traditional lamina one. This paper investigates the touch case of a yarn with others around it at interior of three dimensional 4 directional (4D) rectangular composite preform braided by 4 step 1∶1 procedure. The distribution rule of contact points on the yarn and a distinguishing feature of force transmission among the yarns at fabric interior are found. The related geometry parameters and a new kind of finite element for interior yarn are determined. They are useful to the researches on this materials structure geometry, micromechanics as well as finite element analyses.