  Spin nematic order is investigated for a S=1 spin model on triangular lattice
with bilinear-biquadratic interactions. We particularly studied an antiferro
nematic order phase with three-sublattice structure, and magnetic properties
are calculated at zero temperature by means of bosonization. Two types of
bosonic excitations are found. One is a gapless excitation with linear energy
dispersion around $k \sim 0$, and this leads to a finite spin susceptibility at
T=0 and would have a specific heat $C(T) \sim T^2$ at low temperatures. These
behaviors can explain many of characteristic features of recently discovered
spin liquid state in the triangular magnet, NiGa2S4.
