  We investigate the entanglement dynamics of bipartite quantum system between
two qubits with the dissipative environment. We begin with the standard
Markovian master equation in the Lindblad form and the initial state which is
prepared in the extended Werner-like state: $\rho^{\Phi}_{AB}(0)$. We examine
the conditions for entanglement sudden death (ESD) and calculate the
corresponding ESD time by the Wootters' concurrence. We observe that ESD is
determined by the parameters like the mean occupation number of the environment
$N$, amount of initial entanglement $\alpha$, and the purity $r$. For
  N=0, we get the analytical expression of both ESD condition and ESD time. For
$N>0$ we give a theoretical analysis that ESD always occurs, and simulate the
concurrence as a function of $\gamma_0t$ and one of the parameters $N, \alpha$,
and $r$.
