  We report photometric and spectroscopic observations of the SU UMa-type dwarf
novae, KS Ursae Majoris, during its 2003 February superoutburst. Modulations
with a period of $0.07017\pm0.00021$ day, which is 3.3% larger than the orbital
period, have been found during the superoutburst and may be positive
superhumps. A maximum trough-to-peak amplitude of around 0.3 magnitude is
determined for this superhump.
  The spectra show broad, absorption-line profiles. The lines display blue and
red troughs which alternate in depth. The radial velocity curve of the
absorption wings of H$\beta$ has an amplitude of $40\pm11$ km s$^{-1}$ and a
phase offset of $0.12\pm0.03$. The $\gamma$ velocity of the binary is $3\pm9$
km s$^{-1}$ and varies on an order of 50 km s$^{-1}$ from day to day. From
another clear evidence for a precessing eccentric disk, we obtain a solution to
an eccentric outer disk consistent with theoretical works, which demonstrates
the validity of the relation between superhumps and tidal effects. The inner
part of the disk is also eccentric as evidenced by asymmetric and symmetric
wings in the lines. Therefore, the whole disk is eccentric and the variation of
$\gamma$ velocity and the evolutionary asymmetric line profiles could be
criterions for an precessing eccentric accretion disk.
