\documentclass[12pt]{standalone}

\usepackage{tikz}
\usepackage{ctex}

\begin{document}
\begin{tikzpicture}

\matrix[column sep={3cm,between origins}]
{
    \scoped[<-,every node/.style={circle,draw}]
    \node {1}
        child {node {2}}
        child {node {3}
            child {node {4}}
            child {node {5}}}; &
    \scoped[<-,every node/.style={circle,draw}]
    \node {6} child {node {7} child {node {8}}}; \\
};

\end{tikzpicture}
\end{document}
