Abstract: Borax (0.4%, 0.6% and 0.8%) and ammonium molybdate (0.05%, 0.07% and 0.09%) were used to study their effect on seeds yield of alfalfa in squaring stage, initial blooming stage and full blooming stage through leaf spraying. The result indicated that boron and ammonium molybdenum could significantly increase the seeds yield. For as ammonium molybdate, 0.05% was the most proper concentration, and the seeds yield, pods number per inflorescence, branch number and seeds per pod were increased by 35%, 54.37%, 10.96%, and 35.68% respectively. 0.8% was the best concentration for borax as and the seeds yield was increased by 15.56%.