A synchronous system for a three-stage ball bearing slide includes a carrier track being inserted into a fixed track to carry a mobile track. Both of the mobile and the carrier tracks engage in reciprocal movement along the same axis direction in relation to the fixed track. A dancer is pivoted to the rear end of the carrier track. The carrier track synchronously slides with the mobile track by a protruding tongue on the mobile track upholding the dancer, and is held in position by having the dancer to uphold a compression bit on the fixed track. A direct push on the extreme where the carrier track is extended releases the dancer from the compression bit to retract once again the carrier track into the fixed track.