A numerical analysis of structural stresses and strains fields in unidirectional fibrous composites was made. These composites have quasi-periodic structure because the position and orientation of materials’ structural elements have a random technological deviation in a transversal plane. The computer synthesis algorithm of quasi-periodic structures was made. These algorithms take into the consideration the laws of distribution of the material’s geometrical parameters of elements. The statistic analysis of structural fields, stresses and strain that depend on geometric characteristics of reinforcement elements’ value deviation was made. For constructions of these materials, the estimation of micro-destructions probability was made.