  The cosmological inflow of a galaxy is speculated to be able to enter the
galaxy and enhance the star formation rate (SFR) and black hole accretion rate
(BHAR). In this paper, by performing high-resolution hydrodynamic simulations
in the framework of {\it MACER}, we investigate the fate of the inflow and its
impacts on the evolution of a massive elliptical galaxy. The inflow properties
are adopted from the cosmological simulation IllustrisTNG. We find that, the
inflow gas hardly enters but is blocked beyond $\sim 20$ kpc from the central
galaxy and becomes part of the circumgalactic medium (CGM). The gas pressure
gradient, mainly contributed by the thermalized stellar wind and subdominantly
by the energy input from the AGN, balances gravity and prevents the inflow from
entering the galaxy. The SFR and BHAR are almost not affected by the normal
inflow. However, if the rate of cosmological inflow were increased by a factor
of 3, a small fraction of the inflow would enter the galaxy and contribute
about 10\% of the gas in the galaxy. In this case, the gas density in the
galaxy would increase by a factor of $\ga$ 20. This increase is not because of
the additional gas supply by the inflow but the increase of gas density in the
CGM caused by the inflow. Consequently, the SFR and BHAR would increase by a
factor of $\sim$ 5 and $\sim 1000$ respectively. Finally, AGN feedback can
perturb the motion of the inflow and heat the CGM through its intermittent
outbursts.
