  We study loop operators of $5d$ $\mathcal{N}=1$ SYM in $\Omega$ background.
For the case of U(1) theory, the generating function of correlation functions
of the loop operators reproduces the partition function of melting crystal
model with external potential. We argue the common integrable structure of $5d$
$\mathcal{N}=1$ SYM and melting crystal model.
