[en] The three-wave interaction in a laser beat-wave accelerator is studied. We find that with the parameters of σ = ω/sub p//(ω1-ω2) and β = ω2/ω1 properly chosen (where ω/sub p/, ω1, and ω2 are the plasma frequency and frequencies of the two laser beams, respectively), the required large-amplitude plasma wave will be excited even though the incident laser beams are relatively weak; as a result, the injected electrons will obtain a significant energy gain