The effect of wheel speed on microstructures of Ti-48%Ni (mole fraction) melt-spun ribbons was investigated by X-ray diffractometry,scanning electron microscopy and transmission electron microscopy. When the wheel speed is 26 and 42 m/s,the as-spun ribbons are completely crystallized to the Ti-Ni B2 phase. The Ti-rich plate precipitates lying on {100} planes are observed in the as-spun ribbon fabricated with a wheel speed of 26 m/s. The spherical Ti2Ni precipitates are observed at grain boundaries in the as-spun ribbons fabricated with a wheel speed of 42 m/s. Amorphous and B2 phases coexist in the as-spun ribbon fabricated with a wheel speed of 52 m/s. The uniformity of grain size in heat treated ribbons decreases with increasing wheel speed.