Based on remote sensing and geographic information system technologies,the effects of altitude and slope factors on the process of land use/cover changes in Sanjiang Plain during 1954-2005 were studied.Results showed that during the past five decades,landuse in Sanjiang Plain changed substantially and cropland increased by 2.25 times.In contrast,wetland,woodland,and grassland decreased considerably.Changes of land use types have different features in altitude classes.Cropland increased mainly at the locations below 200 m,especially at locations below 100 m.Wetland decreased mainly in the same way as cropland in terms of altitude.Woodland and grassland showed a fluctuant changing trend in all altitude classes during different periods.Built-up land changed in all altitude classes,but mainly happened below 200 m.For slope degree,cropland increased at all slope classes and increased mainly at locations below 1°.The area of cropland had a relatively small increase at locations above 10°.Changes of woodland,grassland,and wetland mainly happened on 1° slope degree class.Water body and built-up land also changed mainly at sites with small slope gradients.