the present invention discloses a speculative lookahead processing device and method to enhance the statistical performance of datapaths . the method comprises steps : entering an input signal to at least two datapath units in a round - robin way ; outputting the correct value at the nth cycle , and acquiring the speculation value at the mth cycle beforehand to start the succeeding computation , wherein m and n are natural numbers and m is smaller than n ; comparing the speculation value with the correct value at the nth cycle to determine whether the speculation is successful ; if successful , excluding extra activities ; if not successful , deleting the succeeding computation undertaken beforehand and restarting the succeeding computation with the correct value .