An adapter assembly , comprising: a casing comprising a plurality of side walls , a front cover and a rear cover , wherein the plurality of side walls are connected with each other and disposed between the front cover and the rear cover , the plurality of side walls , the front cover and the rear cover collaboratively define an accommodation space located in the casing , the front cover comprises an opening , a plurality of concaves and a plurality of position-limiting portions , the opening is in communication with the accommodation space , the plurality of concaves are concavely formed from an inner surface of the opening , the plurality of position-limiting portions are disposed on the inner surface of the opening of the front cover , each of the plurality of position-limiting portions is extended from the inner surface of the opening toward a center of the opening , and the plurality of position-limiting portions and the plurality of concaves are arranged alternately; and a plug adapter detachably assembled with the casing and comprising a main body and a plurality of protrusions , wherein the plurality of protrusions are disposed on an outer surface of the main body , and the plurality of protrusions are corresponding in position to the plurality of concaves in a one-to-one relationship; wherein when the plug adapter is assembled with the casing , portion of the main body is disposed in the accommodation space , the other portion of the main body penetrates through the opening and is exposed to the exterior of the accommodation space , each of the plurality of protrusions penetrates through corresponding one of the plurality of concaves and is exposed to the exterior of the accommodation space , and each of the plurality of protrusions exposed to the exterior of the accommodation space is connected with corresponding one of the plurality of position-limiting portions through the rotation of the plug adapter so that the plug adapter is assembled with the casing . a casing comprising a plurality of side walls , a front cover and a rear cover , wherein the plurality of side walls are connected with each other and disposed between the front cover and the rear cover , the plurality of side walls , the front cover and the rear cover collaboratively define an accommodation space located in the casing , the front cover comprises an opening , a plurality of concaves and a plurality of position-limiting portions , the opening is in communication with the accommodation space , the plurality of concaves are concavely formed from an inner surface of the opening , the plurality of position-limiting portions are disposed on the inner surface of the opening of the front cover , each of the plurality of position-limiting portions is extended from the inner surface of the opening toward a center of the opening , and the plurality of position-limiting portions and the plurality of concaves are arranged alternately; and a plug adapter detachably assembled with the casing and comprising a main body and a plurality of protrusions , wherein the plurality of protrusions are disposed on an outer surface of the main body , and the plurality of protrusions are corresponding in position to the plurality of concaves in a one-to-one relationship; wherein when the plug adapter is assembled with the casing , portion of the main body is disposed in the accommodation space , the other portion of the main body penetrates through the opening and is exposed to the exterior of the accommodation space , each of the plurality of protrusions penetrates through corresponding one of the plurality of concaves and is exposed to the exterior of the accommodation space , and each of the plurality of protrusions exposed to the exterior of the accommodation space is connected with corresponding one of the plurality of position-limiting portions through the rotation of the plug adapter so that the plug adapter is assembled with the casing . <EOS>