A novel 2/3 full-speed divider operating at high speed with low power consumption comprising a ECL D flip-flop in master-slave configuration and a phases-selection block is provided in the present invention. The master latch and slave latch comprise a pair of input terminals, a pair of control terminals, and a pair of output terminals. The master latch further comprises two pairs of complementary cross-couple transistors for amplifying the output of the master latch for entering the phase-selection block. The phase-selection block has a pair of input terminals, a clock signal input terminal, and an output terminal generating an output signal adjusted by a division ratio according to the clock signal. The division ratio is either 1/2 or 1/3 and the divider functions as a 2/3 divider.