I set the speak time to every 10 minutes but its respond is dangerously silently quite. More info: because of the removal of Jovie in my distro (Netrunner), I have to sudo apt-get install jovie. At first, it worked well, but after some restarts, it doesn't work anymore.

Which version of kde do you have? Does jovie speak anything else (try right clicking the system tray icon and choosing speak clipboard contents)?

KDE version: 4.11.5, Jovie version: 0.6.0. It seems that Jovie won't speak anymore. I also try to go to its setting, choose speak file but it keeps no respond.

Sounds like the Speech backend might be missing. Is speech-dispatcher installed?

Another thing to try is "spd-say hello" in a terminal. That calls speech-dispatcher directly and should work if speech-dispatcher is installed.
If that works but jovie doesn't try running spd-conf to setup speech-dispatcher again.

Yesterday I had apt-get update and things seem to be find. Don't know if this really solve my problem or just a coincident. Anyway, thank you for helping.

It doesn't work again. The only commands I used yesterday (which I think it might affect a whole system) are apt-get update and apt-get upgrade. Besides, I also deleted some default games.

Which synthesizer is jovie set to use (just the default maybe)? Also, does sdp-say "hello" work? I bet speech-dispatcher crashed or something when it was updated/upgraded probably. Does restarting (or just logging out and back in) help?

It works again without any attempt to fix it. Weird, right?
In spite of that, when I use sdp-say "hello", the terminal appears "command not found" althout speech-dispatcher is already the newest version.