  In this paper, we study the Joule-Thomson expansion for RN-AdS black holes
immersed in perfect fluid dark matter. Firstly, the negative cosmological
constant could be interpreted as thermodynamic pressure and its conjugate
quantity with the volume gave us more physical insights into the black hole. We
derive the thermodynamic definitions and study the critical behaviour of this
black hole. Secondly, the explicit expression of Joule-Thomson coefficient is
obtained from the basic formulas of enthalpy and temperature. Then, we obtain
the isenthalpic curve in $T-P$ graph and demonstrate the cooling-heating region
by the inversion curve. At last, we derive the ratio of minimum inversion
temperature to critical temperature and the inversion curves in terms of charge
$Q$ and parameter $\lambda$.
