We report an exact numerical study on disorder effect in double-Weyl semimetals,and compare exact numerical solutions for the quasiparticle behavior with the Born approximation and renormalization group results.It is revealed that the low-energy quasiparticle properties are renormalized by multiple-impurity scattering processes,leading to apparent power-law behavior of the self-energy.Therefore,the quasiparticle residue surrounding nodal points is considerably reduced and vanishes as ZE ∝ Er with nonuniversal exponent r.We show that such unusual behavior of the quasiparticle leads to strong temperature dependence of diffusive conductivity.Remarkably,we also find a universal minimum conductivity along the direction of linear dispersion at the nodal point,which can be directly observed by experimentalist.