The invention belongs to the design of aircraft engines, and relates to a deceleration and diffusion structure of an inlet of a combustion chamber of an aircraft engine. The structure is integrally composed of an outer ring 1, an inner ring 2 and hollow supporting plates 3, and is formed by connecting the outer ring 1 and the inner ring 2 through the 24 hollow supporting plates 3 distributed uniformly and circumferentially. The deceleration and diffusion structure has the advantages that not only are requirements of a general diffuser met, deceleration and pressurization are performed on an air flow at the inlet of the combustion chamber through an annular expansion passage of the diffuser, but also the inlet adopts a diffuser body with the 24 hollow supporting plates 3 to connect an innershell body with an outer shell body to form a combustion chamber casing, when the engine works and the own axial force of the combustion chamber and the axial force and torque from a high-pressure turbine guider are transmitted forward to a gas compressor casing through a combustion chamber casing inner shell and a combustion chamber casing outer shell, since the inner portion and outer portion of the casing are communicated through the 24 hollow supporting plates 3, an unloading function acts on a diffuser portion, thereby ensuring the safe work of the combustion chamber.