A computational simulation for a nonslender BWB UCAV configuration with rounded leading edge and span of 1.0m was performed to analyze its aerodynamic characteristics at low A.o.A.s. Reynolds number based on the mean chord length is 1.25 million. γ-Re<SUB>θ</SUB> transition model and k-ω SST model was used to assess effect of transition for flow behavior. Also γ transition model that accounts for crossflow instability effects was employed to investigate crossflow instability effects in three-dimensional boundary layer on the UCAV aerodynamic surfaces. After assessing aerodynamic coefficients and lift to drag, it was found that crossflow effects plays an important roles at given flow condition.