\documentclass[a4paper,twoside,fleqn]{book}
%\usepackage{hyperref}
\usepackage{fancyhdr}
\usepackage{graphicx}
\usepackage{subfig}
\captionsetup[subfigure]{labelformat=simple, labelsep=colon}
\usepackage{etoolbox}
% % % % % % % % % % % % % % % % % % %
\usepackage[numbers,sort&compress]{natbib}
\usepackage{standalone}
%\includeonly{context}
\usepackage{pxfonts}
\usepackage{scrextend}
\usepackage{perpage}
\usepackage{xepersian}

\begin{document}
\makeatletter
\patchcmd{\@chapter}{\addcontentsline{toc}{chapter}{\protect\numberline{\thechapter}#1}}{\addcontentsline{toc}{chapter}{\protect{\numberline{\chaptername~\tartibi{chapter} :  #1}}}}{}{}
\long\def\@subcaption#1[#2]#3{%

 \ par
  \addcontentsline{\csname ext@#1\endcsname}{#1}%
    {\protect\numberline{\csname #1name\endcsname{} \csname the#1\endcsname}{\ignorespaces #2}}%
 \begingroup
  \@parboxrestore
    \if@minipage
      \@setminipage
    \fi
    \normalsize
   \@makecaption{\csname fnum@#1\endcsname}{\ignorespaces #3}\par
 \endgroup}

 \newcommand\mydot[1]{\scalebox{#1}{.}}
 \patchcmd{\@dottedtocline}
   {\hbox{.}}
   {\hbox{\mydot{1}}} %تغییر می کند
   {}
   {} 
   % % % % % % % % % % % % % % % % % % % % %55

 \renewcommand*{\@dotsep}{4}

\renewcommand*\l@section{\@dottedtocline{1}{1.5em}{2.3em}}
\renewcommand*\l@subsection{\@dottedtocline{1}{3em}{4.3em}}
\renewcommand*\l@figure{\@dottedtocline{1}{1.5em}{4.3em}}
\let\l@table\l@figure
\let\stdl@chapter\l@chapter
\renewcommand*{\l@chapter}[2]{\stdl@chapter{{#1}}{}}
\makeatother
%\end{comment}
\baselineskip=.8cm
\fontsize{10}{6}\selectfont
\addtocontents{toc}{\hspace{1.5em}\textbf{\underline{عنوان}}}
\addtocontents{toc}{\hfill\textbf{\underline{صفحه}}\par}
\pagestyle{plain}
\addcontentsline{toc}{section}{فهرست مطالب}
\tableofcontents
\cleardoublepage
\chapter{مقدمه}
\section{ساختار}
\chapter{مقدمه2}
\end{document}