Bulk amorphous (Nd0.7Pr0.3)60-xFe30Al10Cux (x=0, 1, 2 , 4) alloys with diameter of 2 mm were prepared by argon arc melting and suction casting the molten alloy into a copper mould. The magnetic properties and coercivity mechanism of the alloys were investigated by the measurement of major hysteresis loop, exchange coupling curve (dM-H plot), magnetic viscosity and the temperature dependence of the coercivity. At room temperature, all the alloys exhibit hard magnetic properties. The coercivity increases slightly with increasing the Cu content, while the remanence has the same values. The fluctuation field, Hf, is determined from sweep rate measurement. It is in the range of 12.1~15.2 mT. The thermal activation volume, va, is from 1.5×10-18 to 1.9×10-18 cm3. The exchange coupling interaction in all four alloys is confirmed by the dM-H plot. The temperature dependence of the coercivity can be well explained by Gaunt’s strong pinning model of domain walls. The hard magnetic behavior of bulk amorphous (Nd0.7Pr0.3)60-xFe30Al10Cux (x=0, 1, 2, 4) alloys may be determined by the exchange coupling interaction among clusters and strong domain wall pinning.