The Nd60Fe20Co10Al10 bulk amorphous alloy was prepared by suction casting into the copper mould. The microstructure and magnetic property of the alloy during crystallization process were studied. The magnetic viscosity of this alloy during crystallization process was investigated by waiting time method. It was found that magnetic properties of the Nd60Fe20Co10Al10 bulk amorphous alloys annealed at temperature below 783 K had a slight change. However, after annealing at temperature higher than 783 K, values of the remanence (Mr), saturation magnetization (Ms) and intrinsic coercivity (iHc) decreased significantly. Furthermore, the alloy showed paramagnetic behavior after annealing at 803 K. When samples were annealed at 703 K and 753 K, the activation volume (Va) and activation diameter (Da) changed slightly, while the fluctuation field (Hf) showed a maximum at 703 K. It was due to the presence of a metastable phase. The relationship of parameters of magnetic viscosity and magnetic property of the Nd60Fe20Co10Al10 alloy was discussed.