Thank you, rct2nut and Nforce.
I've ever thought to use the scenario editor to change the option.
But the tracks in my park is really really hard to re-build again for me, even use the Track Decoder.
There's some pics in my site.
http://coach777.myweb.hinet.net/Some of the scenery was imitated from other's parks, But many of them were made by me.
Thank you all again.