The invention discloses a method to plant Medicago sativa in saline-alkaline soil and improve soil and fertilizer condition. The method comprises: applying an improving fertilizer, plowing, performingrotary tillage and leveling the land, sowing, managing the field, and harvesting, wherein the improving fertilizer is made from desulfurization gypsum, activated carbon, flyash, plant stalk granules,bentonite, zeolite, urea, ammonium phosphate, blast furnace slag particles and a microbial agent having a weight ratio of (30-40):(10-14):(6-10):(16-18):(8-12):(4-8):(3-5):(3-5):(4-6):(1-3). saline-alkaline soil is improved by taking the measures such as saline-alkaline soil improving fertilizer and planting Medicago sativa, the survival rate and yield of Medicago sativa are high, the improving of the whole saline-alkaline soil is excellently effective, and the improving process is green and free of pollution. Therefore, the method is an application technique worthy of wide popularization.