\documentclass[12pt]{standalone}

\usepackage{tikz}
\usepackage{ctex}

\begin{document}
\begin{tikzpicture}

% the coordinates frame

\draw[->] (0,0) -- (0,5);
\draw[->] (6,0) -- (6,5);
\draw[->] (0,0) -- (8,0) node[right] {$w$};

% the plot

\draw[thick] (0,3) node[left] {$d(u,i)$} -- (2,4) -- (6,2) node[right] {$d(v,i)$};

\draw[dashed] (2,0) node[below] {$c(x,0)$} -- (2,4);

\end{tikzpicture}
\end{document}
