Because of the different flexural rigidity between longitudinal and transverse direction, orthotropic plate theory may be suitable for describing the behavior of composite deck. The ratio of flexural rigidity between longitudinal and transverse direction affects the live load moment. Because of the ratio of flexural rigidity of concrete unfilled steel grid deck has a direct relationship with main bearing bar spacing, it is concluded that the study for the distribution factor which is effected by main bearing bar spacing and aspect ratio is needed. In this study, evaluate the live load moment of concrete unfilled steel grid deck using the AASHTO LRFD Bridge Design Specification and presents the distribution coefficient equation for concrete unfilled steel grid deck.