Abstract: In order to investigate the anti-tearing behaviors of envelop thin films with initial cracks, Kevlar fabric reinforced envelope thin films used in stratospheric airships with prefabricated initial crack (PIC) were chosen and the plane stress analysis method of elastic-plastic fracture mechanics was adopted. Considering the effects of slipping friction between warp and weft, the tearing strength and deformation modes of film crack tips were analyzed. Physical model of crack tip tearing and arithmetical tensile deformation computational model based on friction effects were established. The stress distribution of stress concentration area among crack tip was obtained. In order to verify the rationality of the computational model above, specimens with PIC length of 10, 20, 30 and 40 mm were tested to obtain the tearing strength, respectively. Results show that when PIC width ratio does not exceed 0.50, the deviation between calculated values of models and testing values is lower than 4.12%. Compared with the improved stress intensity factor theory, the computational model established above is more accurate, which provides an effective approach for the tearing strength design of stratospheric airship envelope.