External catalytic cracking heater with pre-distributed particles

The invention discloses an external catalytic cracking heater with pre-distributed particles and is suitable for a catalytic cracking device in an oil refinery. The external catalytic cracking heater is characterized in that a plurality of unit type heat exchange tubes (6) with independent water inlets and water outlets are arranged inside an external heater (4); the heat exchange tubes (6) extend from the top to the bottom of the external heater (4), and the bottom of the external heater is provided with a guide bracket (2) which limits transverse swing of the heat exchange tubes (6); the lower parts of the heat exchange tubes (6) are immersed in a dense-phase fluidized bed (11) at the bottom of the external heater (4); hot catalyst particles entering from a catalyst inlet (10) in the middle of the external heater (4) enter an annular fluidized bed (17), and the hot particles uniformly flow into the dense-phase fluidized bed (11) from the upper edge of a side wall (15) on the inner side of the annular fluidi