  We have constrained the charge-mass ($\varepsilon-m$) phase space of
millicharged particles through the simulation of the rotational evolution of
neutron stars, where an extra slow-down effect due to the accretions of
millicharged dark matter particles is considered. For a canonical neutron star
of $M=1.4~M_{\odot}$ and $R=10~{\rm km}$ with typical magnetic field strength
$B_{0}=10^{12}$ G, we have shown an upper limit of millicharged particles,
which is compatible with recently experimental and observational bounds.
Meanwhile, we have also explored the influences on the $\varepsilon-m$ phase
space of millicharged particles for different magnetic fields $B_{0}$ and dark
matter density $\rho_{\rm{DM}}$ in the vicinity of the neutron star.
