Abstract: Paraquat is a better instant efficient and contact poisoning herbicide while atrazine is an ideal systemic effect herbicide.The former two kinds of herbicide were mixed in different ratio to obtain ratio with 90% efficacy.Two methods were used to judge its joint action,the conclusion was different.When Japanese Qianbanyingxiong’ and N.A.Mansour’s judgement methods were used,it indicated antigonism or addition.Nevertheless,both judgement results didn’t show any synergism.