The present invention discloses a data protection unit fireproof layer which comprises an upper shell, a fireproof blanket, an inner shell and a chassis. The upper shell is of a hollow barrel-shaped structure and is provided with an opening formed correspondingly to the chassis; the inner shell is arranged inside a cavity formed by the surrounding of the upper shell and the chassis; and the fireproof blanket is arranged between the inner shell and the cavity. The fireproof blanket is tightly filled between the inner shell and the cavity and no other contact except the fireproof blanket exists between the whole body formed by the marine data protection unit upper shell and the chassis and the inner shell, so that the inner shell is protected from being influenced by an external high temperature in an omnibearing manner. The chassis assembly of the data protection unit fireproof layer is also provided with a positioning apparatus which is fixedly connected with each wire. Data connection and power supply connection are not influenced by other factors.