thanks Michael, it really work.
and another problerm is when i export step from MOI to MAYA the "Nurbs export option" does not have an option like turn z-up to y up. the obj export option has.
but it does't matter, I just turn -90 degree on x-axis in maya or use the second ways you told me and it's all OK.
and I hope there is an option to set y-up or z-up system in MOI, men always get lazy, haha.