Thank you Richard,it's so kind of you to reply.
I had known about the M20 in Junos 6.4 is very old indeed.
and what i have tried to do is a only simple PAT services. just as simple as you did with a router 10 bucks worth.
But i fail,and i research the internet,and i got a result as you had told me :
It's not workable without a AS-PIC.
I do have got a good education after this experiment, it makes me to know the config of Junos ( so "C style" and so "difico")
but thanks dude,you are my teacher too.