The invention discloses a water and oil resistant paper-based composite bag and a production method thereof. The production method comprises the following steps: mixing and stirring trichloromethane, ethylene glycol, n-propanol, polylactic acid and a plasticizer to obtain a coating liquid M; and coating the surface of brown paper with the coating liquid M, and drying the coated brown paper to obtain the water and oil resistant paper-based composite bag. The problem of influences of easy decaying and fragmentation of packaging bags meeting water on the strength of the packaging bags due to the poor water and oil resistance of packaging bags produced of common paper-based composite materials is solved in the invention.