A method for calculating directional pattern of a beam pointing adjustable antenna, the method is performed by a device for calculating directional pattern of a beam pointing adjustable antenna, the device comprises a slot transmission matrix obtaining module, an antenna transmission matrix obtaining module and an antenna directional pattern generating module that are sequentially connected, wherein the slot transmission matrix obtaining module comprises a single-slot waveguide measurement submodule, the beam pointing adjustable antenna comprising a plurality of slot units that generate leaky waves, and the method comprising the following steps: S1. obtaining, by the slot transmission matrix obtaining module, a total transmission matrix of a single-slot waveguide and a transmission matrix of a seamless waveguide corresponding to one of the slot units, and obtaining an equivalent transmission matrix of the single slot unit according to the total transmission matrix of the single-slot waveguide and the transmission matrix of the seamless waveguide; S2. obtaining, by the antenna transmission matrix obtaining module, an arrangement and combination mode of the slot units and a beam pointing control code representing on or off state of each slot unit, and obtaining a transmission matrix cascading mode of the beam pointing adjustable antenna according to the arrangement and combination mode, the beam pointing control code, and a scattering parameter matrix of the single slot unit; and S3. obtaining, by the antenna directional pattern generating module, the directional pattern of the single-slot waveguide structure excited at the left end and the directional pattern of the single-slot waveguide structure excited at the right end, and obtaining a composite directional pattern of the beam pointing adjustable antenna according to the directional pattern of the single-slot waveguide structure excited at the left end, the directional pattern of the single-slot waveguide structure excited at the right end, and the transmission matrix cascading mode of the beam pointing adjustable antenna; evaluating, according to the composite directional pattern of the beam pointing adjustable antenna, electrical performance indicators of a beam pointing adjustable antenna, so as to optimize a selection, arrangement, combination, and spacing of the slot units; performing, by the single-slot waveguide measurement submodule, a two-port test on the single-slot waveguide to obtain the scattering parameter matrix of the single-slot waveguide. S1. obtaining, by the slot transmission matrix obtaining module, a total transmission matrix of a single-slot waveguide and a transmission matrix of a seamless waveguide corresponding to one of the slot units, and obtaining an equivalent transmission matrix of the single slot unit according to the total transmission matrix of the single-slot waveguide and the transmission matrix of the seamless waveguide; S2. obtaining, by the antenna transmission matrix obtaining module, an arrangement and combination mode of the slot units and a beam pointing control code representing on or off state of each slot unit, and obtaining a transmission matrix cascading mode of the beam pointing adjustable antenna according to the arrangement and combination mode, the beam pointing control code, and a scattering parameter matrix of the single slot unit; and S3. obtaining, by the antenna directional pattern generating module, the directional pattern of the single-slot waveguide structure excited at the left end and the directional pattern of the single-slot waveguide structure excited at the right end, and obtaining a composite directional pattern of the beam pointing adjustable antenna according to the directional pattern of the single-slot waveguide structure excited at the left end, the directional pattern of the single-slot waveguide structure excited at the right end, and the transmission matrix cascading mode of the beam pointing adjustable antenna; evaluating, according to the composite directional pattern of the beam pointing adjustable antenna, electrical performance indicators of a beam pointing adjustable antenna, so as to optimize a selection, arrangement, combination, and spacing of the slot units; performing, by the single-slot waveguide measurement submodule, a two-port test on the single-slot waveguide to obtain the scattering parameter matrix of the single-slot waveguide.