In this paper, the
Arnoldi-type process and symmetric Lanczos-type process for solving large scale
quadratic eigenvalue problem (l^2A +lB+C)x=0 are given. One decomposition theorem about the
matrices A, B and C is obtained based on the Householder transformation. The advantage
of the Arnoldi-type process and symmetric Lanczos-type process is that they can
preserve the matrix structure and properties of the original problems. Finally,
some numerical examples are presented to show the efficiency of the proposed
methods.