The utility model discloses a mounting structure of a built-in single-end-face mechanical seal for a pump, which comprises a shaft sleeve and a hoop, one side of the outer side of the shaft sleeve is sleeved with a spring seat, the other side of the outer side of the shaft sleeve is sleeved with a static ring seat, one side of the inner side of the spring seat is sleeved with a moving ring, one side of the moving ring is provided with a fixing piece, and the other side of the moving ring is provided with a sealing ring. A spring is arranged on one side of the fixing piece, a static ring is arranged on the inner side of the static ring base in a sleeved mode, and a positioning block is arranged on one side of the static ring. According to the utility model, through the mutual matching among the static ring seat, the hoop, the static ring, the fixed sheet, the spring, the shaft sleeve, the spring seat and the movable ring, when the device is used for installing the mechanical seal, the mechanical seal, the shaft sleeve and the static ring seat can be pre-installed through the hoop, and the mutual positions are pre-locked, so that the mechanical seal is easy to install and does not shift or slip off; the installation quality is guaranteed, installation of the built-in single-end-face mechanical seal can be completed at a time, labor is saved, and the quality is guaranteed.