The invention provides compound composition containing eugenol and mustard essential oil which are plant-sourced active substances with environmental compatibility and mixed in a weight ratio being (1:10)-(10:1), preferably in a weight ratio being (1:4)-(4:1). The compound composition has an obvious synergic effect, can be prepared in a form such as microemulsion, emulsion in water, water dispersible granules and the like and is used for controlling plant fungal diseases, bacteriosis, virus diseases and the like, so that the control effect is improved, the dosage is reduced, the application times are reduced, the control range is enlarged, the resistance is delayed, the requirement of a conventional dose reduction application technology is met, and the prepared preparation is environmentally friendly and has good application prospect.