This study is experimentally examining initial fire behavior important for evacuation safety in order to establish performance-based fire safety design, centering on combustibles. Relation between fire load and heat release rate was examined through an experiment in order to establish a method that could predict initial fire behavior. Besides, initial fire behavior was investigated through comparison with the results derived from real scale fire experiment by using the conventional studied fire growth rate model. As a result, in case fire load was $12kg/m^2$ or over, it was difficult to be derived by using the conventional dynamics equation, but its regression equation could be derived through experimental study. Also, it was verified that a large effect was produced on the initial fire behavior according to the ignition source and arrangement of combustibles.