  The coupling between the dark components provides a new approach to mitigate
the coincidence problem of cosmological standard model. In this paper, dark
energy is treated as a fluid with a constant equation of state, whose coupling
with dark matter is $\bar{Q}=3H\xi_x\bar{\rho}_x$. In the frame of dark energy,
we derive the evolution equations for the density and velocity perturbations.
According to the Markov Chain Monte Carlo method, we constrain the model by
currently available cosmic observations which include cosmic microwave
background radiation, baryon acoustic oscillation, type Ia supernovae, and
$f\sigma_8(z)$ data points from redshift-space distortion. The results show the
interaction rate in 3$\sigma$ regions:
$\xi_x=0.00328_{-0.00328-0.00328-0.00328}^{+0.000736+0.00549+0.00816}$, which
means that the recently cosmic observations favor a small interaction rate
which is up to the order of $10^{-2}$, meanwhile, the measurement of
redshift-space distortion could rule out the large interaction rate in the
1$\sigma$ region.
