The invention relates to a cable assembly and a cable tray using the cable assembly. The cable assembly comprises a cable and a cable plug disposed at least one end of the cable, the cable plug comprises a plug body the front end of which is an inserting connecting end, the plug body is provided with a contact element, the cable plug further comprises a plug sealed cap, the plug sealed cap comprises a sealed cap body the rear end of which is connected to the front end of the corresponding plug body through a first detachable connecting structure to block off the inserting connection end of the corresponding plug body, and the front end of the sealed cap body is provided with a second detachable connecting structure for being detachably connected with a corresponding plug fixing seat. The problem that the plug contact element is exposed in external environment after the cable plug is taken down from the plug fixing seat in the prior art is solved.