  In this paper we study the quasi-forest simplicial complexes and we define
the concept of simplicial $k$-cycle (denoted by $\mathcal{S}_k$) and simplicial
$k$-point (denoted by $\mathcal{P}_k$). We show that a simplicial complex
$\Delta$ is quasi-forest if and only if it does not have any $\mathcal{P}_k$
and any $\mathcal{S}_k$ for $k\geq 3$. Furthermore we characterize almost
Cohen-Macaulay quasi-forest simplicial complexes. In the end we show that the
cycle graph $G=C_n$ is almost Cohen-Macaulay if and only if
$n=3,4,5,6,7,8,9,11$.
