  Consider the integral equation \begin{equation*}
f^{q-1}(x)=\int_\Omega\frac{f(y)}{|x-y|^{n-\alpha}}dy,\ \ f(x)>0,\quad x\in
\overline \Omega, \end{equation*} where $\Omega\subset \mathbb{R}^n$ is a
smooth bounded domain. For $1<\alpha<n$, the existence of energy maximizing
positive solution in subcritical case $2<q<\frac{2n}{n+\alpha}$, and
nonexistence of energy maximizing positive solution in critical case
$q=\frac{2n}{n+\alpha}$ are proved in \cite{DZ2017}. For $\alpha>n$, the
existence of energy minimizing positive solution in subcritical case
$0<q<\frac{2n}{n+\alpha}$, and nonexistence of energy minimizing positive
solution in critical case $q=\frac{2n}{n+\alpha}$ are also proved in
\cite{DGZ2017}. Based on these, in this paper, the blowup behaviour of energy
maximizing positive solution as $q\to (\frac{2n}{n+\alpha})^+ $ (in the case of
$1<\alpha<n$), and the blowup behaviour of energy minimizing positive solution
as $q\to (\frac{2n}{n+\alpha})^-$ (in the case of $\alpha>n$) are analyzed. We
see that for $1<\alpha<n$ the blowup behaviour obtained is quite similar to
that of the elliptic equation involving subcritical Sobolev exponent. But for
$\alpha>n$, different phenomena appears.
