添加\usepackage{subfigure}宏包。

\begin{figure}[htbp]
\centering
\subfigure[Throughput]{
	\label{Fig.sub.1}
	\includegraphics[scale=1.47]{test.png}}
\subfigure[Latency]{
	\label{Fig.sub.2}
	\includegraphics[scale=1.47]{test.png}}
\caption{MainfigureCaption}
\label{Fig.lable}
\end{figure}

添加\usepackage{subfigure}宏包。

\begin{figure}[htbp]
\centering
\subfigure[Throughput]{
	\label{Fig.sub.1}
	\includegraphics[scale=1.47]{test.png}}
%添加这个空格才能上下并列显示
\subfigure[Latency]{
	\label{Fig.sub.2}
	\includegraphics[scale=1.47]{test.png}}
\caption{MainfigureCaption}
\label{Fig.lable}
\end{figure}