A new diagnostic method , Om is applied to generalized Chaplygin gas ( GCG ) model as the unification of dark matter and dark energy .
On the basis of the recently observed data : the Union supernovae , the observational Hubble data , the SDSS baryon acoustic peak and the five-year WMAP shift parameter , we show the discriminations between GCG and \Lambda CDM model .
Furthermore , it is calculated that the current equation of state of dark energy w _ { 0 de } = -0.964 according to GCG model .