the code:
\begin{figure}[htbp]
\centering
\includegraphics[width=\textwidth]{figure/1.eps}
\end{figure}
\begin{figure}[htbp]
\centering
\includegraphics[width=\textwidth]{figure/2.eps}
\end{figure}
By the way, the eps figures are exported by tecplot.
the sample blurry figure likes:(only the text on the secondary figure)

12/22/2016,
Thanks @Bernard, it realy is the problem of the fonts. when I change it to the Times New Roman, the text become clear. BUT if I only need the orgin fonts, what can I do to make sure the text is still clear?
\textwidth? – Mico Dec 22 '16 at 10:26