The variation rules of tensile strength and strain at break of the Seaman PVDF8028 biaxial warp knitted membrane and Ferrari 1202T2 membrane at seven biaxial angles of 0^o， 15^o， 30^o， 45^o， 60^o， 75^o and 90^o were compared. The applicability of Tsai Hill strength criterion， Norris strength criterion and Hashin strength criterion to the two kinds of membranes was studied. The off-axis tear patterns and tear characteristics of the two kinds of membranes at 0^o， 15^o， 30^o， 45^o， 60^o， 75^o and 90^o off-axis angles were compared. The biaxial mechanical properties of the two kinds of membranes were compared， and the applicability of linear and nonlinear orthotropic constitutive models to the constitutive relations of the two kinds of membranes was discussed， which can provide theoretical reference for engineering design.