The bandwidth of ultra-thin sheet absorber in low frequency is difficult to broaden; therefore, a thri-square loop nested absorber loaded with resistors is designed in this paper. The substrate with high dielectric is utilized to realize broadening the frequency bandwidth. The theoretical analysis and simulation verification is described. The absorption rate of the absorber between 1.3 GHz and 1.35 GHz is more than 90% and the peak of the absorption rate is about 1.33 GHz; the absorber is insensitive to polarization and achieves high absorption rate in wide incidence angle. The effect of thickness and dielectric constant of the substrate on the absorber performance is analyzed briefly.