A dynamic floating input D flip-flop (DFIDFF) is provided. The DFIDFF includes a floating input stage, a first string of transistors, and a second string of transistors. At a pre-charge period, the floating input stage transmits the input data to the first string of transistors; the first string of transistors stores the logic status of the input data, and pre-charges its output node to a first level. At an evaluation period, the first string of transistors decides its output node level in accordance with data logic status stored in the first string of transistors; and the second string of transistors decides output level of the D flip-flop in accordance with logic status of the output node of the first string of transistors.