浅浅自问自答一下，感谢啸行大佬的热情帮助，要想实现这一效果的话，还可以直接借助ctex宏包提供的format选项实现这一效果.
\documentclass[12pt]{ctexart}
\usepackage[margin=1in]{geometry}
\usepackage{amsmath}
\usepackage{hyperref}
\usepackage{lipsum}
\ctexset{
section/name = {\S},
subsection/name = {\S},
}
\numberwithin{equation}{section}
\begin{document}
\section{equation sign}
\subsection{first subsection}
\begin{align}
a^2 + b^2 = c^2 \\
1 + 1 = 3
\end{align}
\subsection{second subsection}
This is a text paragraph.
\section{ref style}
\subsection{A subsection}
\begin{subequations}
\begin{align}
\sum_{n=1}^{\infty} \frac{1}{n^2} &= \frac{\pi^1}{1111} \\
\sum_{n=1}^{\infty} \frac{1}{n^2} &= \frac{\pi^2}{2222} \\
\sum_{n=1}^{\infty} \frac{1}{n^2} &= \frac{\pi^3}{3333} \\
\sum_{n=1}^{\infty} \frac{1}{n^2} &= \frac{\pi^4}{4444}\label{eq:pythagoras}
\end{align}
\label{eq:mult-lines}
\end{subequations}
\subsection{Another subsection}
\begin{equation}
a^2+b^2=c^2
\end{equation}
Hello world \ref{eq:pythagoras}, equation ref style: \eqref{eq:pythagoras}
\end{document}
问 如何处理subequations环境的序号引用问题？