A tent top folding and unfolding mechanism includes a connecting seat, a sliding seat, connecting rods, an elastic member and a bolt. The connecting seat is to be pivotally connected with tent top rods, and includes a sinking seat extending downward. The sliding seat is disposed below the connecting seat and movable in an upward and downward direction with respect to the connecting seat. The sliding seat includes an accommodating seat for receiving the elastic member. The sinking seat of the connecting seat has an inner diameter greater than an outer diameter of the accommodating seat to receive the accommodating seat. Each connecting rod has one end pivotally connected to a lower portion of the sliding seat and the other end to be pivotally connected to a corresponding tent top rod. The bolt passes through the connecting seat and the elastic adjustable member, and is fastened at the lower end.