Lito Yap
Ansys Employee

@Zhaoyu Zhang,

Try to run this sample API script (i.e. save as 'lumtest.py'); 

import lumapi
fdtd = lumapi.FDTD()
fdtd.addfdtd()
fdtd.addring()
fdtd.addmesh()
fdtd.save("lumtestpy.fsp")

from the "CAD > Script file editor" window. With Python Integration showing "Active". (see image) 

If it works and runs to completion, it will save the file, "lumtestpy.fsp" on your current working directory (cwd).