A broadband acoustic wave diffusion structure, comprising a plurality of acoustic wave diffusion units, wherein each acoustic wave diffusion unit comprises at least one acoustic wave propagation section, and at least one acoustic wave diffusion unit further comprises an acoustic wave focused section communicating with the acoustic wave propagation section; the acoustic wave focused section is formed by an acoustic wave focused cavity filled with an isotropic or anisotropic material (4,5), the acoustic wave focused cavity is a through cavity with variable cross-section, one end of the through cavity is closest to the acoustic source, and is the incidental face of acoustic waves from the acoustic source; the other end of the through cavity communicates with the acoustic wave propagation section; wherein acoustic waves from the acoustic source first enter the acoustic wave focused cavity from one side, and are focused by the variable section cavity and the acoustic material filled therein, and then, the focused acoustic waves enter the acoustic wave propagation section and continue to travel; wherein the acoustic wave propagation section is formed by an acoustic wave propagation passage with two ends; one end of the passage is open and communicates with the acoustic wave focused cavity of the acoustic wave focused section, as the entrance of the acoustic wave propagation section; the other end of the passage is closed; acoustic waves from the acoustic wave focused cavity continue to travel in the acoustic wave propagation passage; and further wherein in different acoustic wave diffusion units, the acoustic wave propagation passages have different lengths; some acoustic wave diffusion units have no acoustic wave focused section, and only comprise the acoustic wave propagation sections, in which case, the open end of the acoustic wave propagation passage is closest to the acoustic source and is the entrance of acoustic waves from the acoustic source to the acoustic wave diffusion unit; some acoustic wave diffusion units comprise acoustic wave focused sections and acoustic wave propagation sections, in which case, one end of the acoustic wave focused section is closest to the acoustic source and is the incidental face of acoustic waves from the acoustic source; for the acoustic wave diffusion unit comprising the acoustic wave focused section and the acoustic wave propagation section, the acoustic wave propagation passage of the acoustic wave propagation section is arranged through the measures of bending, coiling or stacking in a monolayer or multilayer or spatial spiral structural form, and occupies part or whole of available space of the broadband acoustic wave diffusion structure; as a result, the maximum length of the acoustic wave propagation passage may be dozens or even hundreds of times of the thickness of the broadband acoustic wave diffusion structure. the acoustic wave focused section is formed by an acoustic wave focused cavity filled with an isotropic or anisotropic material (4,5), the acoustic wave focused cavity is a through cavity with variable cross-section, one end of the through cavity is closest to the acoustic source, and is the incidental face of acoustic waves from the acoustic source; the other end of the through cavity communicates with the acoustic wave propagation section; wherein acoustic waves from the acoustic source first enter the acoustic wave focused cavity from one side, and are focused by the variable section cavity and the acoustic material filled therein, and then, the focused acoustic waves enter the acoustic wave propagation section and continue to travel; wherein the acoustic wave propagation section is formed by an acoustic wave propagation passage with two ends; one end of the passage is open and communicates with the acoustic wave focused cavity of the acoustic wave focused section, as the entrance of the acoustic wave propagation section; the other end of the passage is closed; acoustic waves from the acoustic wave focused cavity continue to travel in the acoustic wave propagation passage; and further wherein in different acoustic wave diffusion units, the acoustic wave propagation passages have different lengths; some acoustic wave diffusion units have no acoustic wave focused section, and only comprise the acoustic wave propagation sections, in which case, the open end of the acoustic wave propagation passage is closest to the acoustic source and is the entrance of acoustic waves from the acoustic source to the acoustic wave diffusion unit; some acoustic wave diffusion units comprise acoustic wave focused sections and acoustic wave propagation sections, in which case, one end of the acoustic wave focused section is closest to the acoustic source and is the incidental face of acoustic waves from the acoustic source; for the acoustic wave diffusion unit comprising the acoustic wave focused section and the acoustic wave propagation section, the acoustic wave propagation passage of the acoustic wave propagation section is arranged through the measures of bending, coiling or stacking in a monolayer or multilayer or spatial spiral structural form, and occupies part or whole of available space of the broadband acoustic wave diffusion structure; as a result, the maximum length of the acoustic wave propagation passage may be dozens or even hundreds of times of the thickness of the broadband acoustic wave diffusion structure.