An improved zoom lens mechanism is disclosed which allows the outer diameter of the zooming assembly to be reduced. It contains: (a) a focusing ring having a plurality of focusing pins; (b) a first barrel with longitudinal slots which is interconnected with a rear portion of the focusing ring, and contains a plurality of transverse slots at a front portion thereof respectively matching the positions of the focusing pins, the first barrel also contains a plurality of diametrically disposed longitudinal slots; (c) an outer ring disposed at the front portion the first barrel, the outer ring is provided with a plurality of second straight slots providing passages for the focusing pins; (d) an inner ring disposed at a rear portion of the outer ring, the inner ring is attached at a rear end of the first barrel, the inner ring is interconnected with the outer ring, both the inner and outer rings are provided with a plurality of beads; and each of the beads penetrates through the longitudinal straight slot; and (e) a second barrel with spiral slots which is disposed at an outer portion of the first barrel, the second barrel has a front end portion which is provided with a plurality of first contour holes for receiving respective beads disposed within an inner ring, the front portion of the second barrel is also provided with a second and third contour holes which are disposed adjacent to the first contour hole.