An impact angle constrained nonsingular fast terminal sliding mode guidance law (NFTSMGL) based on fixed-time disturbance observer(FxTDO) is designed in the presence of uncertain disturbances. FxTDO is used to accurately estimate the internal and external disturbance in the process of missile interceptor. In order to attenuate the chattering and ensure the convergence of guidance system within finite time, a NFTSMGL method is adopted. The stability analysis is carried out. The simulation results show that FxTDO-NFTSMGL can be used to converge the guidance system at a limited time and meet the requirements of maneuvering target interception. Compared with NFTSMGL, the guidance law has a fast convergence speed and avoids the chattering problem.