We study the following integral system with negative exponents:
$$\left\{\begin{array}{c}u\left(x\right)={\int}_{{\mathbb{R}}^{n}}xy{}^{\alpha n}{v}^{p}\left(y\right)\phantom{\rule{0.3em}{0ex}}dy,\phantom{\rule{1em}{0ex}}\hfill \\ v\left(x\right)={\int}_{{\mathbb{R}}^{n}}xy{}^{\alpha n}{u}^{q}\left(y\right)\phantom{\rule{0.3em}{0ex}}dy,\phantom{\rule{1em}{0ex}}\hfill \end{array}\right.$$ 
with
$\alpha >n$,
$p,q>0$ and
$\frac{1}{p1}+\frac{1}{q1}=\frac{\alpha n}{n}$. Such
a nonlinear integral system is related to the study of the best constant of the reversed
Hardy–Littlewood–Sobolev type inequality. Motivated by work of Dou, Guo and Zhu
(Adv. Math. 312 (2017) 1–45) where they used the improved method of moving
planes, we prove that each pair of positive measurable solutions is radially symmetric
and monotonic increasing about some point. Our result is an extension of the work for
$\alpha <n$,
$p,q<0$
of Chen, Li and Ou (Comm. Partial Differential Equations 30:1–3 (2005),
59–65).
