The invention relates to a mixed weed killing agent with glufosinate ammonium and diguat dibromide. The mixed weed killing agent is compounded by the following raw materials by weight percent: 1-99.99% of glufosinate ammonium and 0.01-99% of diguat dibromide, wherein the glufosinate ammonium is from one or more in glufosinate-ammonium technical material, glufosinate-ammonium sodium salt, glufosinate-ammonium potassium salt, glufosinate-ammonium trimethyl sulfonium salt, glufosinate-ammonium ammonium salt and glufosinate-ammonium isopropylamine salt. The mixed weed killing agent is compounded by screening the diguat dibromide and the glufosinate ammonium; the diguat dibromide has the contact-poisoning action, and the contact-poisoning action can not hinder the absorption of the glufosinate ammonium by leaves, not only is the effect of the glufosinate ammonium not influenced, but also the synergistic effect is achieved for the effect of the glufosinate ammonium, the weed killing time can be shortened for 3-10 days, and the cost of the pesticides is reduced by 10%, so that the mixed weed killing agent has the characteristics of economy and high efficiency.