NOVELTY - Recycling formic acid solvent in metronidazole production process, comprises evaporating hydroxylation liquid using an evaporator to obtain dilute formic acid vapor; removing formic acid vapor in metronidazole and other cosolvent; passing viscous polyphosphate and high concentration phosphoric acid downstream of absorbent tower packing layer, and removing a portion of water in the formic acid vapor; passing phosphorus pentoxide via pipeline for further removal of water in the formic acid vapor; and condensing the concentrated formic acid vapor.    USE - The method is useful for recycling formic acid solvent in metronidazole production process (claimed).    DETAILED DESCRIPTION - Recycling formic acid solvent in metronidazole production process, comprises (i) evaporating hydroxylation liquid using an evaporator to obtain dilute formic acid vapor with concentration of 30-70 mass%; (ii) passing the formic acid vapor into cold filler layer via top of the evaporator or feeding cold hydroxylation liquid into downstream of filler layer, and removing formic acid vapor in metronidazole and other cosolvent; (iii) passing viscous polyphosphate and high concentration phosphoric acid downstream of absorbent tower packing layer, and removing a portion of water in the formic acid vapor; (iv) passing phosphorus pentoxide via pipeline for further removal of water in the formic acid vapor; and (v) condensing the concentrated formic acid vapor in a condenser into high concentration formic acid liquid. An INDEPENDENT CLAIM is also included for a device for recycling formic acid solvent in metronidazole production process, comprising an evaporator (1), storing kettle (7), a water absorption tower (8), a condenser (12) and a storage tank (16), where the upper part of the evaporator is provided with a filler and inlet valve; the filler and the storage tank are connected via a pipeline; the vertical section of the filler is made of nylon mesh, and a porous tube is inclined slightly upward in two parts of the horizontal section; the horizontal section is provided with high position groove on the lower end and a condenser at the bottom; the high position groove bottom is provided with a perforated pipes and screw; the condenser is provided with a condenser inlet port, which is connected to the absorption tower outlet end portion of the horizontal section; and a control valve connected to the storage tank via pipeline.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the device for recycling formic acid solvent in metronidazole production process.    Evaporator (1)    Storing kettle (7)    Water absorption tower (8)    Condenser (12)    Storage tank (16)