  We report the results of the analysis of an AstroSat observation of the Black
Hole candidate MAXI J1535-571 during its Hard Intermediate state. We studied
the evolution of the spectral and timing parameters of the source during the
observation. The observation covered a period of $\sim$5 days and consisted of
66 continuous segments, corresponding to individual spacecraft orbits. Each
segment was analysed independently. The source count rate increased roughly
linearly by $\sim$30 %. We modelled the spectra as a combination of radiation
from a thermal disk component and a power-law. The timing analysis revealed the
presence of strong Quasi Periodic Oscillations with centroid frequency
$\nu_{\rm{QPO}}$ fluctuating in the range 1.7-3.0 Hz. We found a tight
correlation between the QPO centroid frequency $\nu_{\rm{QPO}}$ and the
power-law spectral index $\Gamma$, while $\nu_{\rm{QPO}}$ appeared not to be
correlated with the linearly-increasing flux itself. We discuss the
implications of these results on physical models of accretion.
