Ramie fiber was treated with amino silicone oil. The properties of ramie fiber were investigated with IR, contact angle test, XRD, and TG. The results have shown that some silicone molecules were coated on the surface of the modified ramie fiber, and it reduced the number of hydroxyl groups on the ramie surface. The crystallinity of ramie fiber was increased by 15%, and the water absorption of the modified ramie fiber was decreased, inducing a better compatibility between ramie fiber and polypropylene. In addition, the weight of the unmodified fiber had a loss of 5% before 230 ℃, while the modified ramie fiber had no decomposition virtually, so that the heat resistance of the modified ramie fiber has been greatly improved.