The invention relates to a rectifying and vacuum-pumping system and technology in production processes of benzoic acid. The system comprises a rectifying tower, a Roots vacuum pump, a pipe bundle condenser and a toluene pump, wherein a toluene layered automatic recovery device is arranged between the pipe bundle condenser and the toluene pump. After the vacuum-pumping gas is condensed by the condenser, toluene and steam in the gas are condensed into a liquid mixture to enter the toluene layered automatic recovery device, and then, the liquid mixture moves forward under the action of 2-5 grades of hydraulic barriers in a flow pushing way; in the last one or two chambers of the recovery device, the toluene and water are completely layered, and the toluene floats at the upper layer of the water level; with the increase of the liquid mixture entering the recovery device, the toluene automatically flows into a toluene storage tank from the upper openings of the chambers to be recovered; and the layered water is communicated with a water outlet pipe under the action of gravity to automatically flow out of the toluene layered automatic recovery device. The invention changes the technological processes of the rectifying and vacuum-pumping system in the production processes of the benzoic acid, and fully recovers the raw material toluene, thereby saving the raw material. The invention brings considerable economic benefit to the TianJin DongDa Chemical Industry Co.,Ltd., brings social benefit to the society, reduces the pollution and protects the environment.