  We study the quasisymmetric geometry of the Julia sets of McMullen maps
$f_\lambda(z)=z^m+\lambda/z^\ell$, where $\ell$, $m\geq 2$ are integers
satisfying $1/\ell+1/m<1$ and $\lambda\in\mathbb{C}\setminus\{0\}$. If the free
critical points of $f_\lambda$ are escaped to the infinity, we prove that the
Julia set $J_\lambda$ of $f_\lambda$ is quasisymmetrically equivalent to either
a standard Cantor set, a standard Cantor set of circles or a round
Sierpi\'{n}ski carpet (which is also standard in some sense). If the free
critical points are not escaped, we give a sufficient condition on $\lambda$
such that $J_\lambda$ is a Sierpi\'{n}ski carpet and prove that most of them
are quasisymmetrically equivalent to some round carpets. In particular, there
exist infinitely renormalizable rational maps whose Julia sets are
quasisymmetrically equivalent to round carpets.
