Normal fly ash (PC ash) and circulating fluid bed ash (CFB ash), which with same diameter distribution and different physicochemical characteristics were used to filled nature rubber, and properties of natural rubber compound was investigated. The results showed that: 100% Modulus, Permanent deformation and Hardness Reinforced of natural rubber compound were increased. CFB ash has a better reinforcing effect than that of PC ash. It is because that CFB ash ( porous surface) have more junction with natural rubber than that of PC ash (solid spherical particles), and carbon residue in CFB ash play a reinforcing effect like carbon black. KH550 modified fly ash has better reinforcement effect than original ash.