We discuss the relevance of long wavelength excitations for the low energy spectrum of QCD, and try to develop an efficient method for solving the Schrödinger equation, and for extracting the glueball masses and long wavelength functions of the ground and excited states. Some technical problems appearing in the calculations of SU(3) gauge theory are discussed.QCD in the pure gauge sector possesses a nontrivial vacuum structure and bound states called glueballs. Solving the Schrödinger equation in the Hamiltonian formulation can directly provide not only the glueball masses from the eigenvalues, but also the profiles, i.e., the wave functions for the ground state and excited states.Strictly speaking, the continuum physics should be extracted in the asymptotic scaling region predicted by the renormalization group equation. In [1, 2, 3, 4, 5], we developed an efficient eigenvalue equation method with some new truncation schemes which preserve the continuum limit. This is an essential step towards the scaling.Our starting point is to obtain the long wavelength wave functions of the ground and excited states. The philosophy is to keep the correct long wavelength limit during the truncation. The low energy spectrum originates mainly from the long wavelength excitations. This is because the size or the Compton length of a glueball, which is usually of the same order as that of a hadron or the lattice size, should be much greater than the lattice spacing a. It is worth mentioning that the confinement of gluons or static quarks is closely related to the long wavelength structure of the vacuum. For the long wavelength configurations U , 1