To address the issues of limited degrees-of-freedom for interference suppression and inter-element mutual coupling in a uniform linear array, this paper proposes an adaptive beam forming method for unmanned aerial vehicle (UAV) navigation based on maximum inter-element spacing constraint (MISC) coarray interpolation. This method aims to increase the number of degrees-of-freedom for interference suppression and reduce the mutual coupling effects between antenna elements. The MISC array covariance matrix is vectorized, and a difference coarray is constructed. Due to the presence of holes in the difference coarray, it is interpolated to form a virtual uniform linear array. An optimization problem based on atomic norm minimization is formulated and transformed into a convex optimization problem. By solving this problem, the signal vector of the interpolated virtual uniform linear array (IVULA) can be recovered. The IVULA signal covariance matrix has a Toeplitz structure, and by exploiting the subspace rotation-invariant property, the directions of all signals can be computed. The covariance fitting method is employed to estimate the powers of all signals. The interference plus noise covariance matrix of the MISC array is reconstructed, the steering vector of the desired signal is predicted, determining the beam forming weight vector for the UAV navigation receiver. Simulation experiments demonstrate that the proposed method is suitable for MISC arrays, outputs higher signal-plus-interference-to-noise ratios than current methods, and exhibits good robustness to model errors.