The magic “tomorrow ring” is also known as magic knot, or “the merry matrimony”. When the ring is in free fall, the closed chain within will quickly knot to fasten the ring. Due to the rapid knotting process of “tomorrow ring” magic, (less than 80 milliseconds), the interesting mechanics behind are rarely known. In this paper, a high-speed camera array experiment platform composed of four high-speed cameras is used to photograph and reconstruct the key process of chain knotting in the magic of “tomorrow ring”. The quantitative analysis of the movement of the ring and the chain found that the key mechanical principle of the success of magic is the whipping effect, enabling it to complete the knot at a speed that the naked eye can not distinguish.