A Bosonic string model at finite temperature on the gravition g(mu nu) and
the dilaton phi background field is examined. Moreover, the duality relatio
n of energy momentum tensor on high genus Riemann surface is derived. At th
e same time, the temperature duality invariance for the action of string ga
s matter is proved in 4-D Robertson-Walker metric, the string cosmological
solutions and temperature duality of the equations of motion for genus g =
1 and 2 are also investigated.