In this paper, polyolefin elastomer (POE) nanofibers were prepared by island melt spinning. The processing temperature range was determined by thermogravimetric analysis to avoid thermal degradation of the material. The morphology of POE nanofibers was optimized by changing the type of cellulose acetate butyrate (CAB), the ratio of POE/CAB, the processing temperature, and the shear rate. The morphological differences of nanofibers under different process parameters were analyzed, including the average diameter and diameter distribution. The results show that considering the thermal stability of CAB, the temperature of the whole processing process should be lower than 250 ℃, and POE nanofibers with a diameter of about 400 nm can be obtained by using CAB-20 with a melt flow rate close to that of POE. At a processing temperature of 235 ℃, the fiber morphology is optimal, with the smallest diameter and the narrowest distribution. At the processing temperature of 250 ℃, the morphology of POE nanofibers shows a cross-networked structure. The closer the twin-screw shear rate is to 400 s^-1, the better the morphology, the smaller the diameter and the more concentrated the distribution of the prepared POE nanofibers. The lower the component ratio of POE to CAB, the better the fiber morphology, but when the ratio is as low as 5∶95, the fiber diameter becomes thicker and the distribution wider.