Abstract: To prepare rubber compound with excellent properties, such as tensile strength, tear strength, hot tear strength and striking heat resistance property, a study was made on micro-fiber of EPDM/PA. It was the first time to find that after some parts of carbon black were replaced by ternary-nylon-copolymer(nylon6/66/1010=20/10/70), mechanical properties of this compound vulcanized by peroxide, especially hot tear could be improved magnificently, while the composite keeping striking heat resistance property. SEM shows that disperse particles could be changed into micro-fibers through some special treatment. Micro-fibers are disorderly oriented in one plane which is vertical to the direction of vulcanization's tension. Only a few micro-fibers become irregular through vulcanizing. Physical test reveals that elongations at break along the lengthways direction are larger than elongations at break along the vertical direction, which is contradictionary to the law of short fiber rubber composite. The reason for it was explained.