In order to seek the optimum tied-ridging tillage system with good controlling on soil erosion, and high utilization of precipitation in semi-arid area, a field experiment with a randomized complete block design was conducted on two slopes (5° and 10°) during alfalfa growing season. The experiment was designed to investigate the effects of different tillage systems (ridging without ties and tied-ridging) on soil water storage, plot runoff efficiency, runoff, sediment loss, alfalfa fodder yield and water use efficiency (WUE), and traditional planting (TP) was taken as control. On the 5°slope, compared with TP, average soil water storage, alfalfa fodder yields and the WUE for ridging without ties increased by 9.3 mm, 20.4% and 4.78 kg/(hm2·mm), respectively. The corresponding parameters for tied-ridging increased 15.0 mm, 8.9 % and 4.58 kg/(hm2·mm), respectively. Runoff and sediment loss on the same slope for ridging without ties decreased by 21.9% and 80.8%, respectively, while these two parameters of tied-ridging decreased by 41.2% and 83.3%. On the 10° slope, compared with TP, average soil water storages, alfalfa fodder yields and the WUE for ridging without ties and tied-ridging increased by 11.2 and 16.2 mm, 22.4% and 9.0%, 4.89 and 4.06 kg/(hm2·mm), respectively, while the runoffs and sediment losses of these two tillage systems ridging decreased by 24.8% and 36.4%, 74.5% and 82.0%, respectively. Average plot runoff efficiencies of TP, ridging without ties and tied-ridging were 11.6%~14.1%, 9.2%~10.0% and 6.7%~7.8%, respectively. Soil water storage in 5° slope increased by 4.3 mm compared with slope of 10°. The differences of net fodder yield, actual fodder yield and WUE between 5° and 10° slopes were not distinct. The runoff, sediment loss and plot runoff efficiency of 10° slope were 1.2 times greater than those of 5° slope. Ridge-furrow rainwater harvesting was good on water and soil conservation, and fodder yield increasing. Tied-ridging was particularly effective for water and soil conservation, while ridging without ties was particularly effective for increasing of fodder yield.