  The anomalous momentum and doping dependence of the electron spectral
function and electron dispersion for copper oxide materials in the underdoped
regime are studied within the t-J model. It is shown that the electron spectrum
is changed with dopings, and the electron dispersion exhibits a flat band
around ($\pi$,0) point in the Brillouin zone, which leads to the normal-state
pseudogap formation. The theoretical results are consistent with the
experiments and numerical simulations.
