# How reduce the space between title and article

\def\maketitle{\par
\begingroup % to make the footnote style local to the title
\def\thefootnote{\fnsymbol{footnote}}
\def\@makefnmark{$^{\@thefnmark}$}
\twocolumn[\@maketitle] \@thanks
\endgroup
\setcounter{footnote}{0}
\let\maketitle\relax \let\@maketitle\relax
\gdef\@thanks{}\gdef\@author{}\gdef\@title{}\let\thanks\relax}
\def\@maketitle{\vbox to \titlebox{\hsize\textwidth
\linewidth\hsize \vskip 0.625in minus 0.125in \centering
{\LARGE\bf \@title \par} \vskip 0.2in plus 1fil minus 0.1in
{\def\and{\unskip\enspace{\rm and}\enspace}%
\def\And{\end{tabular}\hss \egroup \hskip 1in plus 2fil
\hbox to 0pt\bgroup\hss \begin{tabular}[t]{c}\Large\bf}%
\def\AND{\end{tabular}\hss\egroup \hfil\hfil\egroup
\vskip 0.25in plus 1fil minus 0.125in
\hbox to \linewidth\bgroup\Large \hfil\hfil
\hbox to 0pt\bgroup\hss \begin{tabular}[t]{c}\Large\bf}
\hbox to \linewidth\bgroup\Large \hfil\hfil
\hbox to 0pt\bgroup\hss \begin{tabular}[t]{c}\Large\bf\@author
\end{tabular}\hss\egroup
\hfil\hfil\egroup}
\vskip 0.3in plus 2fil minus 0.1in
}}

The above is the style code.

How can I reduce the space between title and the main body?

The vertical extent of the title and author block is controlled by

\vbox to \titlebox{

so your class appears to have a register of that name that you can set with

\setlength\titlebox{...}

The skip at the end

\vskip 0.3in plus 2fil minus 0.1in

may as well just be \vss as it can not work as intended as in a vbox that is forced to a fixed height like this, the skip in that position may affect whether the box is over or under full but won't actually affect the space after the title.

Please always post complete documents not fragments, as otherwise answers such as this one have to make a lot of guesses (that might not be correct)