  For a $hypergraph$ $\mathcal{G}=(V, E)$ with a nonempty vertex set
$V=V(\mathcal{G})$ and an edge set $E=E(\mathcal{G})$, its $adjacency$ $matrix$
$\mathcal {A}_{\mathcal{G}}=[(\mathcal {A}_{\mathcal{G}})_{ij}]$ is defined as
$(\mathcal {A}_{\mathcal{G}})_{ij}=\sum_{e\in E_{ij}}\frac{1}{|e| - 1}$, where
$E_{ij} = \{e\in E\, |\, i, j \in e\}$. The $spectral$ $radius$ of a hypergraph
$\mathcal{G}$, denoted by $\rho(\mathcal {G})$, is the maximum modulus among
all eigenvalues of $\mathcal {A}_{\mathcal{G}}$. In this paper, we get a
formula about the spectral radius which link the ordinary graph and the
hypergraph, and represent some results on the spectral radius changing under
some graphic structural perturbations. Among all $k$-uniform ($k\geq 3$)
unicyclic hypergraphs with fixed number of vertices, the hypergraphs with the
minimum, the second the minimum spectral radius are completely determined,
respectively; among all $k$-uniform ($k\geq 3$) unicyclic hypergraphs with
fixed number of vertices and fixed girth, the hypergraphs with the maximum
spectral radius are completely determined; among all $k$-uniform ($k\geq 3$)
$octopuslike$ hypergraphs with fixed number of vertices, the hypergraphs with
the minimum spectral radius are completely determined. As well, for $k$-uniform
($k\geq 3$) $lollipop$ hypergraphs, we get that the spectral radius decreases
with the girth increasing.
