\documentclass[nofonts]{ctexart}
\setCJKmainfont{Microsoft YaHei}
\begin{document}
中文
\end{document}

This is XeTeX, Version 3.1415926-2.2-0.9995.2 (TeX Live 2009/Debian)
entering extended mode
(./text.tex
LaTeX2e <2009/09/24>
Babel <v3.8l> and hyphenation patterns for english, usenglishmax, dumylang, noh
yphenation, pinyin, loaded.
(/usr/share/texmf-texlive/tex/latex/ctex/ctexart.cls
Document Class: ctexart 2012/04/16 v1.10 ctexart document class
(/usr/share/texmf-texlive/tex/latex/ctex/opt/ctex-options.def
(/usr/share/texmf-texlive/tex/latex/oberdiek/kvoptions.sty
(/usr/share/texmf-texlive/tex/latex/graphics/keyval.sty)
(/usr/share/texmf-texlive/tex/generic/oberdiek/kvsetkeys.sty
(/usr/share/texmf-texlive/tex/generic/oberdiek/infwarerr.sty)
(/usr/share/texmf-texlive/tex/generic/oberdiek/etexcmds.sty)))
(/usr/share/texmf-texlive/tex/latex/etoolbox/etoolbox.sty
(/usr/share/texmf-texlive/tex/latex/etex-pkg/etex.sty))

! Package keyval Error: setkeys undefined.

See the keyval package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                             
                                                 
l.7 [email protected], [email protected], setkeys=\kvsetkeys}
                                                 
? ^C! Interruption.
\GenericError  ...                               
                                                  \endgroup
l.7 [email protected], [email protected], setkeys=\kvsetkeys}
                                                 
?