Abstract: In 1997～1999， a three-year field experimental study on the environmental effect of terraced farmland construction on the arid hillside land in Guizhou karst mountainous areas was conducted. The experimental results showed that soil & water erosion, stone & sand spread and desertification can be prevented, which makes good preparation for returning farmlands to forests and grassland on the slope land with more than 25°. The crop yield of the arid hillside land with less than 25° can be increased by twenty percent(20%), which provides good conditions for slope farm land to return farmland to forest and grass. This arid hillside land terraced technology is simple and feasible with less investment and quick return.