  We revisit the long-standing problem of supersymmetric grand unified theory
(GUT), the doublet-triplet splitting problem. We discuss whether symmetry which
controls the {\mu} term in the minimal supersymmetric standard model is
compatible with GUT. We find that the symmetry must be broken at the GUT scale.
A similar argument also shows that the R symmetry, which is important for low
energy supersymmetry, must be broken down to a Z2R symmetry at the GUT scale.
We propose a new prescription to achieve the doublet-triplet splitting by
symmetry. There, the symmetry which controls the {\mu} term is spontaneously
broken at the GUT scale by order parameters which are charged under other
symmetries. Bilinear terms of triplet Higgses are charged under the other
symmetries, while those of doublet Higgses are not. Then triplet Higgses
directly couple to the order parameters and hence obtain GUT scale masses,
while doublet Higgses obtain suppressed masses. The broken R symmetry can be
also effectively preserved by a similar prescription. As a demonstration, we
construct an SU(5)$\times$SU(5) GUT model. We also comment on unification of
yukawa couplings.
