The Co43Fe20Ta5.5B31.5 amorphous ribbons were prepared by melt spinning. The effects of the crystallization under isothermal and non-isothermal conditions on microstructure and magnetic properties were investigated using X-ray diffraction (XRD), differential thermal analyzer (DTA), and vibrating samples magnetometer (VSM). It is found that the saturation magnetization Ms and the coercivity Hc increase with increasing of the crystallized volume fraction α under the condition of isothermal annealing. The Hc value of the alloy changes from 1.25×79.6 A/m for as-cast sample to 634.45×79.6 A/m for sample annealed at 928 K for 55 min, and at the same time the Ms value changes from 37.2 to 58.4 (A·m2)·kg-1. In the initial crystallization stage, the primary crystallization product is (Co, Fe)21Ta2B6 crystal, and the values of Hc and Ms increases gradually with increasing of α. Along with the development of crystallization, the values of Hc and Ms increase sharply when (Co, Fe)B and (Co, Fe)3B2 crystals precipitate. Under the non-isothermal crystallization conditions, the value of Ms increases monotonously with increasing of the stopping temperature, but the increase amplitude is very small. The value of Hc varies substantially with increasing of the stopping temperature, and the varying is non-monotonous. Within the temperature range of the first crystallization peak, the value of Hc increases monotonously with increasing of the stopping temperature. When the stopping temperature is higher then that of ending of the second crystallization peak, the value of Hc decreases drastically. When the stopping temperature increases from 968 to1153 K, the values of Ms and Hc increase from 61.74 to 67.7 A·m2/kg and from 267.6×79.6 to 416.2×79.6A/m, respectively. The Hc value decreases to 152.2×79.6 A/m when stopping temperature is up to 1273 K