Add the following lines in your preamble
\makeatletter
\RenewDocumentCommand{\section}{sm}{%
\par\addvspace{2.5ex}%
\phantomsection{}% reset the anchor for hyperrefs
\addcontentsline{toc}{section}{#2}%
\parbox[t]{\hintscolumnwidth}{\strut\raggedleft\raisebox{\baseletterheight}{\color{color1}\rule{\hintscolumnwidth}{0.95ex}}}%
\hspace{\separatorcolumnwidth}%
\parbox[t]{\maincolumnwidth}{\strut\sectionstyle{#2}\hspace{\separatorcolumnwidth}%
\strut\raisebox{\baseletterheight}{\color{color1}\rule{\maincolumnwidth-\widthof{\sectionstyle{#2}}-\separatorcolumnwidth}{0.95ex}}}%
\par\nobreak\addvspace{1ex}\@afterheading}% to avoid a pagebreak after the heading
\makeatother
to achieve what you want.
MWE (notice that I've added the option sans
to moderncv
since you're loading sourcesanspro
):
\documentclass[10pt,a4paper,sans]{moderncv}
\moderncvtheme[blue]{classic}
\usepackage[utf8]{inputenc}
\usepackage{color}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[inner=1.2cm,outer=1.2cm,top=0.4cm,bottom=0.4cm]{geometry}
\usepackage{sourcesanspro}
\renewcommand*{\sectionfont}{\Large\bfseries\scshape}
\makeatletter
\RenewDocumentCommand{\section}{sm}{%
\par\addvspace{2.5ex}%
\phantomsection{}% reset the anchor for hyperrefs
\addcontentsline{toc}{section}{#2}%
\parbox[t]{\hintscolumnwidth}{\strut\raggedleft\raisebox{\baseletterheight}{\color{color1}\rule{\hintscolumnwidth}{0.95ex}}}%
\hspace{\separatorcolumnwidth}%
\parbox[t]{\maincolumnwidth}{\strut\sectionstyle{#2}\hspace{\separatorcolumnwidth}%
\strut\raisebox{\baseletterheight}{\color{color1}\rule{\maincolumnwidth-\widthof{\sectionstyle{#2}}-\separatorcolumnwidth}{0.95ex}}}%
\par\nobreak\addvspace{1ex}\@afterheading}% to avoid a pagebreak after the heading
\makeatother
\firstname{\Large{Aaaa}}
\familyname{\Large{\textsc{Bbbb}}}
\title{\normalsize Iiiiiiiiiiiii }
\address{\textbf{113 iiiii}}{\textbf{000 Vvvvv}}
\mobile{\textbf{0000000}}
\email{[email protected]}
\extrainfo{\textbf{bla bla}}
\begin{document}
\pagestyle{empty}
\maketitle
\section{Experience}
\end{document}
Output
