The present invention provides a connection apparatus for sealing a cable, and a communications terminal box. The connection apparatus includes a hollowly disposed enclosure, a clamping part is disposed in the enclosure, and the clamping part is located between a first end and a second end of the enclosure. A first communicating part through which the cable passes is disposed on a first sealing kit, the first sealing kit enters the enclosure from the first end, and moves towards the second end of the enclosure in an axial direction. The clamping part squeezes the first sealing kit, so that the first communicating part wraps and seals the cable. In addition, the clamping part wraps and seals the first sealing kit, so that the cable is sealed in the enclosure. The deformed first sealing kit is detachably fastened in the enclosure by using a first fastening structure, so that the cable is installed. This structure can be repeatedly opened, so that detachment is convenient, a driving power supply is not required, and an installment scenario is not limited. Further, the communications terminal box does not need to be repeatedly flipped when the cable is led in. Therefore, in comparison with an existing mechanism, installment can be simplified and installment efficiency can be improved.