The invention discloses a double-Y type fuel treble atomization method and an atomizer thereof. The atomization method is as follows: high-speed vapor passes through an air inlet and is tangent with fuel oil sprayed out by an oil inlet nozzle at the horizontal direction, oil drops are atomized and mixed and then are tangent again with the high-speed vapor jetted out by an air inlet at the other horizontal direction so as to be atomized and mixed further, the mixture is jetted into a furnace by a pore of a mixing pore for carrying out atomization further. The atomizer comprises an oil-vapor transport segment (1) and an oil-vapor mixing segment (2), the oil inlet nozzle (4) and two air inlets are arranged in the oil-vapor transport segment, wherein, an included angle is formed between the air inlet (3) at the upper part and the oil inlet nozzle, the air inlet (5) at the lower part is in parallel with the oil inlet nozzle and arranged below the oil inlet nozzle (4), the air inlets at theupper part and the lower part are communicated, and a mixing chamber (6) arranged in the oil-vapor mixing segment is communicated with the air inlet below the oil-vapor transport segment. By the tangential force action of the double-Y type structural high-speed vapor and multiple atomization of the jet mixing of the trumpet pore of the oil-vapor mixing segment and the like, the particle sizes of the oil drops are thinner and can even be 30 Mum, thus improving the atomization efficiency.