The flying wing configuration unmanned aerial vehicles (UAVs) employ a highly blended aerodynamic design, which effectively reduces radar cross-section and have better stealth performance. However, due to the absence of a conventional tail wings, flying wing UAVs exhibit low lateral-directional aerodynamic stability and poor controllability. They are prone to pitch/roll coupling and unintended motion during air disturbances or rapid changes in angle of attack, potentially leading to lateral-directional instability and even loss of attitude control. Therefore, taking the Double delta wing configuration UAV as the research object, this study employs a combination of wind tunnel experiments and numerical simulations to investigate the single-degree-of-freedom wing rock characteristics and pitch/roll coupling instability in flying wing configuration UAVs. Firstly, the model was established for both experimental and computational analysis, defining the numerical and experimental methodologies; Then, longitudinal dynamic aerodynamic characteristics of the flying wing configuration under typical conditions were analyzed; Next, the high-angle-of-attack wing rock characteristics were examined through experimental analysis; Lastly, the study explored pitch/roll coupling dynamic instability characteristics in the flying wing configuration. The results indicate that at high angles of attack of 25°, the UAV may exhibit limit cycle wing rock oscillations, while at lower angles of attack, it is more susceptible to lateral motion or unintended pitch/roll coupling.