The effects of the quenching speed on the phase composition and morphology of the Sm-Fe alloy ribbons are measured and analyzed by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (HRTEM). It was found that the size of alloy ribbons decrease along the width and thickness direction firstly with the increasing of quenching speed and maintain stability in the thickness direction even increasing the speed sequentially. The size of agglomeration also decreases in the free surface,about 0.5~3μm as the quenching speed is up to 36m/s. The XRD and EDS results show that there are three different phases in the ribbons: Sm₂Fe₁₇, α-Fe and Sm-rich phase,the main phase grain size of the ribbons is on the sub-micron scale (d^_aver≈340nm, 36m/s), which is restricted not only by the wheel speed but also by the bare two element type. It is the first time to characterize the grain morphology by different methods.