Abstract: The abrasive erosion of polymers has been intensively investigated.In order to reveal the mechanism of abrasive erosion further and to predicate the wear of material,it is necessary to study the physical process theoretically.Based upon analysising the particale trajectories in annular fluid field,it has been found that the abrasive erosion of annular pipe is deve-loped in two stages:impact erosion stage and wet abrasion stage,Moreover,the later is themain wear process. The wear mechanism of wet abrasion for the polyurethane is rnainly as-cribed to surfacial fatigue wear resulting from the sliding friction. On the basis of this result,atheoretical wear equation of abrasive erosion in annular pipe has been derived,in which wearrate of polyurethane is proportional to surface energy per unit area and to an exponent of 3 ofthe flow velocity,however ,it is inversely proportional to an exponent of 3 of the tensitlestrength. This theoretical result which reveals the basic correlation among the material property,running condition and wear characteristic is in accord with the experimental data obtainedpreviously and can be used for predicting the wear of material.