Mode properties of parallel dielectric nanowires coated with graphene are analyzed by using the multipole method. The effects of the operating frequency, the geometrical parameters of the dielectric nanowires, and the Fermi energy of the graphene on the effective refractive index and the propagation length are investigated in detail. The results show that mode properties can be easily adjusted by changing the operating frequency and the Fermi energy of graphene. In addition, the radius or the spacing can be used to adjust mode properties within the range of 50 nm. However, the effects of the two parameters decrease gradually when their values continue to increase. The comparison shows that the analytical results of the multipole method are in good agreement with the numerical results of the finite element method.