The invention belongs to the technical field of wastewater treatment and discloses a method and a device for improving wastewater treatment biological film forming efficiency, aiming to solve the problems of low film forming efficiency, high cost and low applicability in the prior art. The device comprises a magnetic stirrer, a three-neck flask is arranged on the magnetic stirrer, a bacterial solution is fed into an ultrafiltration cross-flow filter device from a lower sample inlet of the ultrafiltration cross-flow filter device through a bacterial solution feeding port and a first peristaltic pump pipeline, and a sample outlet of the ultrafiltration cross-flow filter device is connected with an excretion feeding head of a reactor through a second peristaltic pump. The method and the device have the advantages that different quick film forming means are selected according to the content of homoserine lipid materials under same conditions, high film forming efficiency, low cost and high applicability are realized, effective film forming is realized to the greatest extent, integral film forming time is shortened, and the risk of adopting a packing process is minimized.