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 \pm 0.00021 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 \pm 11 km s ^ { -1 } and a phase offset of 0.12 \pm 0.03 .
The \gamma velocity of the binary is 3 \pm 9 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 .