dear Jenifer_gao
I have some experience with the EKV model...
you can get pretty good matching from low to moderate gate voltages (relative to the process). At high gate voltrages, the lack of second order mobility model makes it more difficult to get a good match both in linear and saturation region. It is usually relatively easy to get a pretty good match for wide/long and wide/short. Getting the same model to match well for narrow/wide and narrow/short is more difficult. However, in general, the gm/id curve will give good results, even if the voltages are not perfectely matched, since it is inherent to the model.
A refernce on general usage of the EKV model:
h**p://legwww.epfl.ch/ekv/workshop/pdf/2_EKV_UMW04_Patrick_Mawet.pdf