  We report on our study of QCD thermodynamics with 2+1 flavors of dynamical
quarks. In this proceeding we present several thermodynamic quantities and our
recent calculation of the critical temperature. In order to investigate the
thermodynamic properties of QCD near the continuum limit we adopt improved
staggered (p4) quarks coupled with tree-level Symanzik improved glue on $N_t=4$
and 6 lattices. The simulations are performed with a physical value of the
strange quark mass and light quark masses which are in the range of
$m_q/m_s=0.05-0.4$. The lightest quark mass corresponds to a pion mass of about
150 MeV.
