caizixian:
How can I tell whether there's keylogger is my system(windows linux)?
Well, as "GoForSmoke" indicated, that is the difficult part.
The first part of this, is to ensure that one never gets in there.
Using Linux is a significant first step, because you do not run virus vacuums (also known as "Internet Explorer") as "root".
With Firefox, you run "NoScript" ("Scriptno" on Chrome) set up so that no site may run scripts until and unless you permit it to. "Adblock Plus" is an excellent idea also because apart from profoundly affecting the usability of less than helpful sites, many viruses are "dropped" in advertising as well as - you would expect, from porn sites.
Similarly, using Thunderbird for email not only allows you to manage your files properly, but has quite strong protection against activating links in emails (for which the "preview" function on that M$ one, whatever it is called, is infamous). Again, on Linux, you are not using a script-enabled PDF reader as a "dropper".
Now I presume you are referring to keylogger software, "accidentally" introduced into your OS, as against company-installed monitoring systems inserted by your employer, or hardware keyloggers physically installed by the NSA. 