Abstract: To clarify wear mechanism of double screwy roller grinded-paste machine,worn surfaces of transport and grinded-paste screwy sheath were examined by means of scanning electronic microscope(SEM) and optical microscope.Result shows that positive screwy sheath can send rotating pulp into chassis and is doesn't bear too much extrusion stress,but because there is lots of erosive liquid in the pulp,main failure mechanism is erosion and abrasion is secondary.Grinded-paste negative screwy sheath itself has no positive transport ability and pulp forms the high-pressure district under function of positive transport package.Very large frictional force that produced between fibre and pulp caused fibre separation and then resulted in silk broomed and routed.Water content in the pulp is very low.Main failure mechanism is high stress abrasive with erosion abrasion at the same time.