Abstract: Aircraft fuel tanks may encounter structural failure under sloshing and vibration excitations, leading to economic loss and casualties. Therefore, evaluating the response of fuel tank under sloshing and vibration is necessary in airworthiness certification. The existing airworthiness certifications are mostly based on high-price and time-consuming full-scale experiments. Numerical studies focusing on regular-shaped fuel tank structure are incapable of modeling the sloshing and vibration behaviors for irregular-shaped tank. In this paper, with a composite wing fuel tank as object, the VOF approach and the modal superposition method are adopted to respectively characterize fluid sloshing and solid vibration, the fluid-solid coupling and sloshing-vibration de-coupling are considered to evaluate the strains in walls of fuel tanks, and the failure analysis of composite structure is carried out by using the maximum strain criterion. This paper gives the time-domain response of both the amplitude and distribution of strains in walls of fuel tank according to different fuel loads, as well as the sloshing/vibration frequency and amplitude. It is found that the sloshing-induced failures are mostly located at the near-tip region of the bottom skin of tank, the vibration-induced damages mostly occur at the near-root region of the bottom skin of fuel tank, and the vibration factor plays a dominant role. This paper has verified the feasibility of replacing the full-scale experiment with numerical simulation for airworthiness certification, and considered the nonlinear relationship between strains in walls of fuel tank and fuel load, sloshing/vibration frequency and amplitude, which provides a useful guidance for airworthiness certification.