Abstract: ‍ ‍For aircraft flexible array radar space time adaptive processing application scenario， a three-dimensional （3-D） wing flexible array is designed in this paper. Three deformation modes of array transverse length change， array longitudinal width change and array surface height change are completed by the changing the array structure parameters. The space-time clutter signal model is constructed based on the relationship between array elements space position vector and array structure deformation parameter set according to the deformable structure of circular arc. For three deformable modes of 3-D wing flexible array， the spatial steering vector and spatial temporal clutter covariance matrix are derived， and the non-Toeplitz structure of clutter covariance matrix is proved by the theory of matrix block nesting， which specifically analysis the elements in different matrix blocks by matrix block decomposition. Through the analysis of the correlation between the Doppler domain and the space frequency domain， the essential mechanism for manifesting the clutter distribution of the 3-D wing flexible array radar in the four-dimensional space is revealed. Different from the traditional airborne array radar， the space-time clutter property of the wing flexible array radar depends on the sampling range in the elevation dimension. The numerical simulation results demonstrate that the spatial temporal clutter of 3-D wing flexible array radar has non-stationary characteristics， for which the space time clutter power spectrum needs to be observed in four-dimensional space. It can be concluded that longitudinal width variation and surface height variation affect the eigenspectrum of space-time clutter more seriously than transverse length variation. Range ambiguity has a more significant effect on deterioration of space-time clutter in the wing flexible array radar. The clutter degree of freedom （DOF） and clutter correlation can be effectively affected by array deformation， which provides a theoretical basis for clutter suppression method based on the optimization of flexible array structure and a theoretical support for airborne deformable array radar technology.