The passive mode-locked erbium-doped fiber laser based on nonlinear optical loop mirror operating in the dissipative soliton resonance (DSR) region is reported. Square wave pulse output is obtained in the abnormal and normal dispersion regimes respectively. At anomalous dispersion regime, the net cavity dispersion is calculated to be -0.32ps 2. Stable square pluses with maximum temporal pulse duration of 33ns are obtained when the pump power is adjusted to 481.2mW. Correspondingly, the single pulse energy is 12.4nJ. Subsequently, a 7m long dispersion compensating fiber is employed to compensate the cavity dispersion to make the laser system work at the normal dispersion regime and the net cavity dispersion is 2.85ps 2. Under the same pump power, the maximum temporal duration of the square pulses is 34.3ns and the single pulse energy is 9.42nJ. It is shown that DSR square pulses can be generated at both anomalous and normal dispersion regimes under the conditions of balanced cavity parameters. Additionally, the influence of the pump power on the time domain width and single pulse energy of square wave pulse is also studied. The results show that the time domain width and single pulse energy of square wave pulse change linearly with the increase of pump power.