Abstract: According to the microstructure of the thick-wall fiber cells of wild oat awns, a mechanical model of filament-wounded anisotropic tubular body was established and the constitutive relation of the fibroblasts under humidity load was derived. The effects of the microfibril angle, cell wall thickness and humidity conditions on strain and stress distribution were also analyzed. The results show that the anisotropic expansion of the filament-wound structure during the moisture changing can cause axial elongation and circumferential torsion of the tubular body. By comparing the relationship between deformations and microfibril angle, it is found that the microfibril angle of the model with stable deformation is laid in the range of 60°-80°.