According to the new method of optimizing the fibers arrangement and orientation in ultra-high performance concrete, the load imposed on the building element to be manufactured with defined dimensions is calculated using common methods and based on this known load, the distribution of tensile stress in this building element is determined. Subsequently, the tensile stress distribution in the given building element is determined by creating a computer geometric model of this building element, and the volume of the geometric model of the building element is split by a spatial mesh system into small discrete volumes from the group of shapes cube, cuboid, pyramid. Then, both the magnitudes of tensile stresses, and spatial vectors of the tensile stresses directions at individual discrete nodes of the mesh are determined. Based on data obtained as described above, are designed both the directions of reinforcements at individual discrete nodes of the mesh given by the resulting direction of the tensile stress, and also the diameters of individual reinforcement fibers corresponding to the magnitudes of these tensile stresses. The resulting spatial reinforcement mesh is modeled by means of a CAD software and printed out using the Direct Metal Laser Sintering 3D metal printing method in case of metal fibers and in case of plastic fibers using one of the 3D printing methods from the group Selective Laser Sintering SLS, Fused Deposition Modeling FDM, or Stereolithography SLA. The produced spatial reinforcement mesh is inserted into the formwork as a substitute for the freely distributed fibers, ultra-high performance concrete is poured in, and when it hardens, the final building element is demoulded.