  So far, the theories of the cuprate pseudogap may be broadly divided into two
main schools of though. One is based upon the idea that view the pseudogap as
deriving from some of precursor superconductivity. Another assumes that
associate the pseudogap phenomena with magnetic pairing of some sort. Both the
scenario of superconducting fluctuation and the scenario of magnetic pairing of
some sort on the pseudogap in underdoped cuprate are based upon the idea that a
fluctuation of a certain type exists at temperatures higher than the usual
superconducting transition temperature and has an effect on the single particl
self-energy and just such a self-energy leads to the gap-like structure of the
spectral weight. In this paper we argue that although a fluctuation of a
certain type has an effect on the origin of the pseudogap, it is not the
crucial factor of the origin of the pseudogap in underdoped cuprate. We
analysis the scenario of the pseudogap in the underdoped cuprate based on the
model that can bring about the spin density wave (SDW) and find the new
dispersion characteristics of the high temperature cuprate superconductors
(excepting two different saddle points located at ($\pm\pi$, 0) and (0,
$\pm\pi$)) and suggest that the pseudogap formation might been due to the
unique interior of the underdoped cuprate.
