The invention relates to a multi-effect biological pesticide aqueous solution agent and a preparation method thereof. The multi-effect biological pesticide aqueous solution agent is characterized in that the agent contains 5-50 percent of pesticide active ingredient plant essence oil, 5-50 percent of simple organic carboxylic acid with a synergistic effect, 5-50 percent of pesticide assistant and 10-85 percent of water, wherein the plant essence oil is one or a mixture of wintergreen oil, camphor tree oil, clove oil, peppermint oil, eucalyptus oil, citionella oil, tea tree oil, lemongrass oil and cinnamon oil, the simple organic carboxylic acid with the synergistic effect is one or a mixture of formic acid, acetic acid and propionic acid, and the pesticide assistant is one or a mixture of dodecylbenzene sulfonic acid, Tween-80, Span-80 and OP-10. The agent can be used for insect killing, insect expelling, sterilization and antivirus in mosquito repelling, family agriculture, family flowering, organic agriculture and green agriculture.