Airbag deployment simulation has been utilized as an important technique to predict the occupant protection performance in the development and design stages. One of the key elements of airbag deployment behavior is the gas flow behavior of jets from inflator. In this study, in order to understand the gas flow behavior of disk type inflator for driver side airbag, visualization experiments were conducted using the schlieren method. The gas flow from the inflator with a retainer has been found to have a strong directivity. Then, the gas flow simulation was conducted with a general purpose finite element program, LS-DYNA, it was possible to obtain a good reproducibility. For reproduction, it was found that jet direction and cone angle of gas diffusion were essential elements. Furthermore, comparison between simulation and experiments were conducted for deployment behavior of driver side airbag, the effect of gas flow on deployment behavior was analyzed. It was found from the results that the reproduction of gas flow from inflator was a major factor for reproduction on deployment behavior of driver side airbag.