  We consider multiscale stochastic dynamical systems. In this article an
\emph{intermediate} reduced model is obtained for a slow-fast system with fast
mode driven by white noise. First, the reduced stochastic system on
exponentially attracting slow manifold reduced system is derived to errors of
$\mathcal{O}(\epsilon)$. Second, averaging derives an autonomous deterministic
system up to errors of $\mathcal{O}(\sqrt{\epsilon})$. Then an intermediate
reduced model, which is an autonomous deterministic system driven by white
noise up to errors of $\mathcal{O}(\epsilon)$, is derived using a martingale
approach to account for fluctuations about the averaged system. This
intermediate reduced model has a simpler form than the reduced model on the
stochastic slow manifold.
