The Invention, which belongs to the building construction field, especially discloses a distribution box support assembly and a method of direct pre-embedded construction by using the same. The distribution box support assembly comprises an adjustable bolt support assembly arranged inside a distribution box, a support frame and a plurality of U-shaped brackets arranged at the outer side of a distribution box back panel. The adjustable bolt support assembly includes two bolt support elements arranged vertically; one bolt support assembly supports the upper wall and the lower wall of the distribution box; and the other bolt support assembly supports the left wall and the right wall of the distribution box. The support frame is arranged at the back panel. A support rod is fixedly arranged between intersection points of the center of the support frame and the two bolt support elements. The distribution box support assembly has characteristics of high correctness of pre embedding and high checking pass percentage.