  The effects of Rashba spin-orbit coupling on BCS-BEC crossover, the
condensate fraction and pair coherence lengths for a two-component attractive
Fermi gas in two dimension are studied. The results at $T=0K$ indicate that (1)
when the strength of SOC is beyond a critical value, BCS-BEC crossover does not
happen in a conventional sense; (2) SOC enhances the condensate fraction, but
suppresses pair coherence lengths.
