  Let $G$ be a simple graph of order $n$, let
$\lambda_1(G),\lambda_2(G),...,\lambda_n(G)$ be the eigenvalues of the
adjacency matrix of $G$. The Esrada index of $G$ is defined as
$EE(G)=\sum_{i=1}^{n}e^{\lambda_i(G)}$. In this paper we determine the unique
graph with maximum Estrada index among bicyclic graphs with fixed order.
