Cu matrix composites with Y

2

O

3

volume fraction of 7% were successfully prepared by liquid phase in situ reactive ball milling and spark plasma sintering（SPS） technique. The effects of ball/material ratio on the microstructure and properties of Y

2

O

3

/Cu composites were investigated by XRD

OM

SEM

universal tensile testing machine

hardness tester and eddy current conductivity meter. The results reveal that with the increase of ball/material ratio

the mechanical performance of in-situ 7 Y

2

O

3

/Cu composites is improved gradually

while the conductivity is decreased slightly

with relative density kept above 97%

achieving basical density. The microstructure indicates that the enhanced phase Y

2

O

3

particles are mainly spherical and the size is between 200 nm and 500 nm. With the increase of ball/material ratio

the second phase particles are more evenly distributed in the copper matrix. The fracture mechanism presents a typical plastic fracture

and Y

2

O

3

particles are obviously distributed in the dimples.