The off axial trapezoid tearing tests of six different types of coated fabrics were carried out, mainly considering 13 off axis angles：from 0 to 900° with interval of 75°. The trapezoid tearing strengths of all kinds of membrane materials at different off axis angles were obtained. The results show that the relevent curves of tearing strength of all membrane materials and different off axis are symentrical at 450° angles, from 0 to 450° and from 450 to 900°,the tearing strength firstly decreases and then increases, the maximum tearing strength is achieved at 450°, the minimum value is at 150° or 225° and 750° or 675°; the off axial trapezoid tearing strength was determined by the strength and the breaking elongation of yarns. Abaqus software is used to conduct finite element method(FEM), the displacement curves before the onset of tearing can be simulated by FEM. The result is fits well with those obtained from tests, and the initial loads of tearing obtained by FEM is also close to those obtained by tests.