Usually i use next simple method: I build Id(Vds) plot, get two point in saturate region and calculate lamda whith next equation:
Lambda = (Id1-Id2)/(Vds1*Id2-Vds2*Id1)
This equation you can conclusion form basic Id=b(Vgs-Vt)^2*(1+Lamda*Vds)
Dear sadegh
you can find lambda just in level 1 model.
because lambda is function of transistor length and many things else.
MikeR's solution is a good way.
regards