A fuel guiderail assembly and an internal damper holder used for the fuel guiderail assembly. The fuel guiderail assembly comprises a fuel guiderail, a first end cap and a second end cap used to close the fuel guiderail, internal dampers, and a first internal damper holder and a second internal damper holder. The internal damper is provided with a first end and a second end. The first end and second end each comprise a main body and a raised part provided on the main body. The holders comprise a clamping part with a slit and a first holding part and a second holding part connected to the clamping part through the first elastic part and the second elastic part, respectively. Said first internal damper holder and second internal damper holder are respectively fixed by the first end cap and the second end cap, and the main bodies of the first end and the second end of the internal dampers are respectively enclosed in the slits of the first internal damper holder and the second internal damper holder so that the internal dampers are prevented from moving in a first direction and a second direction. In addition, the raised parts on the main bodies are blocked by the clamping parts so that the internal dampers are prevented from moving in a third direction and are securely fixed inside the fuel guiderail.