The invention discloses a simulating device for acoustic closed end inlet boundary conditions of a fluid flow system and relates to the field of simulating devices for acoustic closed end inlet boundary conditions. The simulating device comprises a recession cone, a throttle pipe, a diverging cone and a porous diffuser grid, wherein the throttle pipe is of a hollow cylindrical structure; the recession cone and the diverging cone are both in hollow conical structures; the recession cone is fixedly arranged at one axial end of the throttle pipe along the axial direction; in addition, the axialminor-diameter end of the recession cone is fixedly connected with the throttle pipe; the diverging cone is fixedly arranged at the other axial end of the throttle pipe along the axial direction; theaxial minor-diameter end of the diverging cone is fixedly connected with the throttle pipe; the porous diffuser grid is horizontally and fixedly arranged on the major-diameter end face of the diverging cone; besides, the porous diverging cone covers a through hole opening of the diverging cone; the major-diameter end of the recession cone is an inlet section; and the major-diameter end of the diverging cone is an outlet end. According to the simulating device disclosed by the invention, the problems that a traditional structure for simulating the acoustic closed end has over-great flow resistance and is seriously corroded are solved.