  The viscous Cardassian cosmology is discussed, assuming that there is a bulk
viscosity in the cosmic fluid. The dynamical analysis indicates that there
exists a singular curve in the phase diagram of viscous Cardassian model. In
the viscous PL model, the equation-of-state parameter $w_{k}$ is no longer a
constant and it can cross the cosmological constant divide $w_{\Lambda}=-1$, in
contrast with same problem of the ordinary PL model. Other models possess with
similar characteristics. For MP and exp models, $w_{k}$ evolves more near -1
than the case without viscosity. The bulk viscosity also effect the
virialization process of a collapse system in the universe:
$\frac{R_{vir}}{R_{ta}}$ is increasingly large when the bulk viscosity is
increasing. In other words, the bulk viscosity retards the progress of collapse
system. In addition, we fit the viscous Cardassian models to current type Ia
supernovae data and give the best fit value of the model parameters including
the bulk viscosity coefficient $\tau$.
