Abstract: A dust proof assembly of a five communicated tube comprises a bearing; an inner edge of the bearing having an annular recess; a cover being a hollow annular ring; the cover having a buckle corresponding to the annular recess. By above mentioned components, the cover is buckled to the bearing; the buckle of the cover is buckled to the annular recess of the bearing. A seat has a receiving portion; a lower end of the seat being formed with a threaded portion. The bearing and cover is received in the receiving portion of the seat. The cover is a hollow annular ring. The receiving portion has a stepped structure.