  In this paper, we study a class of linear-quadratic (LQ) mean-field games in
which the individual control process is constrained in a closed convex subset
$\Gamma$ of full space $\mathbb{R}^m$. The decentralized strategies and
consistency condition are represented by a class of mean-field forward-backward
stochastic differential equation (MF-FBSDE) with projection operators on
$\Gamma$. The wellposedness of consistency condition system is obtained using
the monotonicity condition method. The related $\epsilon$-Nash equilibrium
property is also verified.
