The complement multiplication processing process includes the following steps: multiplying complement A and complement B in multiplier to obtain result AB; feeding the lower a-1 places of complement A and the sign place y of complement B to selector to obtain result yA; feeding the lower b-1 places of complement B and the sign place x of complement A to selector to obtain result xB; feeding yA and xB separately to the addend-1 input and the addend-2 input of the first adder, setting 0's to lower b places of the addend-1 and setting 0's to lower a places of the addend-2 to obtain the sum 2byA+2axB; and subtracting 2byA+2axB from AB in the second adder to obtain R=AB-(2byAa-1+2axBb-1). Compared with conventional technology, the present invention has one adder saved, and this results in the designed product with small area, low power consumption, low cost and raised calculation speed.