The invention relates to a tray bearing assembly for a machine cabinet, and a screen cabinet and a prefabricated cabin equipped with the same. The tray bearing assembly comprises a moving guide rail which is movably assembled in the machine cabinet body in a front-back direction, wherein an opening end of the machine cabinet body is arranged at the front end; a tray for mounting the corresponding instrument equipment is arranged at the front end of the moving guide rail; the tray is rotationally assembled on the moving guide rail; the rotating central axial line of the tray is perpendicular to the front-back direction; the forward moving travel of the moving guide rail is equipped with an operating station for rotating the back end of the instrument equipment forwardly to the outside of the cabinet body so as to allow an operator to carry out a corresponding operation at the back end of the instrument equipment when the tray rotates along with the instrument equipment. The back end of the instrument equipment can be rotated forwardly to the outside of the cabinet body, so that the operator can carry out the corresponding operation at the back end of the instrument equipment conveniently; and therefore, the operation requirements in different occasions can be satisfied, and a wider application range is achieved.