Because of the performance and cost, airbags are mainly made of coated or uncoated Nylon 66 fabrics. Different airbags, which use different fabrics, vary in the inflation and expansion of the airbag and the protecting function on vehicle occupants. Based on HIC drawn from pendulum impact tests conducted with 45L airbags, the paper analyses influence of some special critical characteristics of airbag fabrics into the performance of airbags. The results show that the weight and the air permeability are the main factors that influence protecting function of airbag. Under the condition of enough fabric strength, light and thin fabric is more preferable in making airbags.