Abstract: Germination rate of the big broad beans soaked under different conditions was studied for optimization.A 4-factor-5-level orthogonal design on concentrations of polyethylene glycol(PEG),boron and molybdenum,and bean soaking time was used for the experiment.The results showed that either by soaking the seeds in a solution containing(a) 24 mgL-1 ammonium molybdate+4 mgL-1 sodium borate+5% PEG for 16 hours,or(b) 8 mgL-1 ammonium molybdate+8 mgL-1 sodium borate+5% PEG for 24 hours,100% germination could be obtained.PEG and soaking time appeared to have the most significant effect on the germination of the big broad beans,and none with the presence of boron or molybdenum.Thus,using 5% PEG to soak the bean seeds for 16 hours was recommended for promoting the germination.