  The chiral symmetry breaking ($\chi_{SB}$) is one of the most fundamental
problems in QCD. In this paper, we calculate quark condensation analytically in
a holographic QCD model dual to the Einstein-Maxwell-Dilaton (EMD) system
coupled to a probe scalar field. We find that the black hole phase transition
in the EMD system seriously affects $\chi_{SB}$. At small chemical potential,
$\chi_{SB}$ behaves as a crossover. For large chemical potential $\mu>\mu_c$,
$\chi_{SB}$ becomes first order with exactly the same transition temperature as
the black hole phase transition by a bypass mechanism. The phase diagram we
obtained is qualitatively consistent with the recent results from lattice QCD
simulations and NJL models.
