The invention provides a method and device for recovering soot generated in the preparation process of copper-phosphorus brazing filler metal. The method comprises the following steps: red phosphorusand copper are put into a graphite crucible of a closed furnace body, nitrogen is introduced, and the copper-phosphorus brazing filler metal is produced by a high temperature reaction; an exhausting system is started, the P2O5 soot generated in the reaction is pumped out, and is sent to a soot absorption reaction tower; a spray system and a tail gas treatment system are started, stainless steel heating rods are started to heat water at the bottom of a tower body to 60 to 80 DEG C, the heated water is transferred to the spray system and water mist is sprayed out through spray nozzles, dropletscondensed by the water mist flow through central circular holes on punching plates of a flow separation system, the high-temperature P2O5 soot is absorbed by water vapor in the soot absorption reaction tower to react to form phosphoric acid to be sunk to the bottom, remaining flue gas is cooled by a cooling and defogging system, and is treated by the tail gas treatment system to be discharged intothe atmosphere, and copper-phosphorus brazing filler metal liquid obtained by the reaction is poured into a mold to prepare a copper-phosphorus brazing filler metal ingot. The method and device provided by the invention can be used for treating a large amount of the P2O5 soot generated in a smelting process, and environmental pollution is avoided.