The utility model discloses a device for continuously processing a waste acid of methyl alcohol low-pressure carbonyl process by using a scrapper thin film evaporator. The device comprises an evaporator, wherein the inlet of the evaporator is connected with a raw material pipeline; a tower top gas phase outlet of the evaporator is in turn connected with a first condenser and a storage tank through a first gas phase pipeline; a tower bottom liquid phase outlet of the evaporator is connected with a storage tank through a first liquid phase pipeline; the outlet of the storage tank is connected with a side line inlet of a first rectifying tower through a transporting pipeline; the tower top gas phase outlet of the first rectifying tower is connected with a rectifying system of an acetic acid producing device through a second gas phase pipeline connected with the second condenser; the tower bottom liquid phase outlet of the first rectifying tower is connected with a rectifying side line outlet of the second rectifying tower through a second liquid phase pipeline; the tower top gas phase outlet of the second rectifying tower is connected with a propionic acid product tank through a third gas phase pipeline of a third condenser. Most of the organic salt and inorganic salt and the condensation compound heavy components which are easy to scab and block the equipment can be eliminated.