[Objectives]  To clone the ATP synthases subunit f gene of Lipaphis erysimi (Kaltenbach) (LeATPf) and assess the effectiveness of RNAi (RNA interference) as a more environmentally-friendly way of controlling L. erysimi. [Methods]  The full-length cDNA sequence of the LeATPf gene was obtained using the reverse transcription technique and expression of the gene silenced using RNA interference. The effect of exposing L. erysimi to a residual film of the RNAi preparation was measured under laboratory conditions, and the effect of spraying the RNAi preparation on L. erysimi in the field was measured in a field experiment. [Results]  The cDNA sequence encoding the LeATPf gene is 324 bp in length, and is more than 90% homologous with the corresponding gene in another five aphid species. The LeATPf gene was mainly expressed in 2nd instar L. erysimi. Spraying aphids with the RNAi preparation effectively inhibited expression of the LeATPf gene. The corrected mortality of L. erysimi following treatment with the RNAi preparation (200.00 mg/L) was not significantly different to that following treatment with 70% imidacloprid after 1, 3 or 5 days (P<0.05). A field experiment indicated that the rate and magnitude of a population’s decline following treatment with the RNAi preparation (50.00, 100.00 or 200.00 mg/L) were not significantly different from the result of spraying 70% imidacloprid after 1, 3 or 7 days (P<0.05). However, the rate and magnitude of population decline using the RNAi preparation were significantly higher than that achieved with 70% imidacloprid on the 14th day after treatment (P<0.05). [Conclusion]  The effectiveness of medium to high concentrations (50.00, 100.00 and 200.00 mg/L) of an RNAi preparation (dsLeATPf) to control L. erysimi was equivalent to imidacloprid, except that the effects of the RNAi preparation lasted longer than that of imidacloprid. The LeATPf gene is a good target for developing an RNA interference preparation to control L. erysimi in the field.