LM285M-2.5 zener diode effect, how should I use it in the analog circuit,

Hello Shuai,

There was no analog circuit attached, so if you are asking a general question on how Zener diodes work, then take a look at this. http://www.egr.msu.edu/classes/ece480/goodman/fall08/group03/appnotes/files/zener_shunt_regulator.pdf

Or you can search the web for tutorials on "How Zener Diodes work?"

If you are having a problem with you circuit, then please post your schematic.

Thanks,