Abstract: Investigations on the effects of different application dosage of Machete and Londax mixture to control weeds in paddy fields showed that applied common and double dosage could effectively control weeds, and the controlling effects exceeded 80% and 90%, respectively, while there were some inhibiting effects to height and branch number of rice, and some resistance of weed had appeared. Weed contest might make rice get some compensation in height and branch under the condition that no herbicide and half dosage were applied, but the rice yield was decreased 36.01% and 54.80%, respectively, mainly because of the decrease of the number of effective panicles and grain number per panicle. The narrow economic benefit of the herbicides should be high.