Sliding rail assembly auto locking structure for drawer

A sliding rail assembly auto locking structure for drawer is disclosed comprised of a holder base, a swivel hook, a slide, two return springs, an actuating block. When an arched block of the swivel hook is approaching a recess in the holder base for positioning, the arched block does not fall to the recess directly, and at this time, oblique guide grooves of the swivel hook are moved over associating guide blocks of the holder base to guide the arched block into the recess slowly and smoothly, and therefore the inner sliding rail of the sliding rail assembly is moved with the drawer smoothly without vibration.