  In this paper, we presented metal abundance properties of 144 M81 globular
clusters. These globulars consist of the largest globular cluster sample in M81
till now. Our main results are: the distribution of metallicities are bimodal,
with metallicity peaks at [Fe/H]\sim-1.51 and -0.58, and the metal-poor
globular clusters tend to be less spatially concentrated than the metal-rich
ones; the metal-rich globular clusters in M81 do not demonstrate a centrally
concentrated spatial distribution as the metal-rich ones in M31 do; like our
Galaxy and M31, the globular clusters in M81 have a small radial metallicity
gradient. These results are consistent with those obtained based on a small
sample of M81 globular clusters. In addition, this paper showed that there is
evidence that a strong rotation of the M81 globular cluster system around the
minor axis exists, and that rotation is present in the metal-rich globular
cluster subsample, while the metal-poor globular cluster subsample shows no
evidence for rotation. The most significant difference between the rotation of
the metal-rich and metal-poor globular clusters occurs at intermediate
projected galactocentric radii. The results of this paper confirm the
conclusion of Schroder et al. that M81's metal-rich globular clusters at
intermediate projected radii were associated with a thick disk of M81.
