In this paper, the 3B flare of February 4, 1986 is studied comprehensi
vely. The escape electrons accelerated to 10-100 keV at the top of cor
onal loop are confirmed by III type bursts. The energetic electron bea
ms moved downward trigger the eruptions in the low layer of solar atmo
sphere. The radio and soft X-ray bursts are interpreted, respectively,
by the maser mechanism and evaporation effect. Finally, the important
role of energetic electron beams in solar flares is pointed out.