  This paper studies the global well-posedness and optimal decay estimates to
the Oldroyd-B model in $\mathbb R^d$ ($d\geq2$). By utilizing the special
structure of this system, we give a simplified proof to the global existence of
solutions for the case of initial data small in critical Besov spaces and
non-small coupling parameters. Moreover, the optimal decay rates of the
solutions under minimal small assumption on the initial data are established by
fully making use of the effect of velocity dissipation and damping mechanism.
