  The lighter scalar tau lepton $\sti$ may be the lightest scalar lepton and
therefore would be found earlier in future collider experiments. We point out
the impact of the measurement of the mass and the mixing angle of $\st$ to
discriminate the models of SUSY breaking. Furthermore, the measurement of the
polarization of $\tau$ lepton($P_{\tau}$) from the decaying $\sti$ helps to
determine the Yukawa sector of minimal supersymmetric standard model. We
present our MC study of the production and the decay of $\sti$ lepton at a
future linear collider at $\sqrt{s}=500$ GeV. The mass, mixing angle of $\sti$
and $P_{\tau}(\sti\rightarrow\tau \chi_1^0)$ would be measured precisely at the
future LC. ( talks given at Yukawa International Seminar(YIKS) '95 on some very
hot and humid day in August, and also at Workshop on {\it Physics and
Experiments with Linear $e^+e^-$ Colliders} Appi, Iwate Japan Sep.8-12 1995.)
