NOVELTY - Catalytic conversion of light hydrocarbon oil comprises allowing the light hydrocarbon oil raw material to enter into a riser pipe reactor at the bottom of a catalytic cracking device, simultaneously allowing a regenerative catalyst to flow from the upper part to carry out catalytic cracking reaction, carrying out separation of the reaction oil gas and catalyst from the resultant from the reactor outlet, further separating to obtain ethylene, propylene, 2-3C alkane, 4C hydrocarbon fraction and other products, separating the regenerated spent catalyst and allowing to enter into a regenerator.    USE - The method is useful for catalytic conversion of light hydrocarbon oil (claimed).    ADVANTAGE - The method: reduces the total surface area of the reaction and regeneration systems to reduce heat dissipation and heat consumption; and solves the problem of inadequate heat generated by coke pyrolysis.    DETAILED DESCRIPTION - Catalytic conversion of light hydrocarbon oil comprises allowing the light hydrocarbon oil raw material to enter into a riser pipe reactor at the bottom of a catalytic cracking device, simultaneously allowing a regenerative catalyst to flow from the upper part to carry out catalytic cracking reaction, carrying out separation of the reaction oil gas and catalyst from the resultant from the reactor outlet, further separating to obtain ethylene, propylene, 2-3C alkane, 4C hydrocarbon fraction and other products, separating the regenerated spent catalyst and allowing to enter into a regenerator to recycle the catalyst. The catalytic cracking device comprises a regenerator (2), a riser pipe reactor (1) of the regenerator, a regeneration riser pipe (9) and a cyclone separator. The outlet of the riser pipe reactor is connected with the inlet of the cyclone separator. A catalyst outlet of the cyclone separator is connected to the regeneration riser pipe. The regeneration riser pipe is set inside the regenerator and opens at the bottom of the regenerator.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of the catalytic cracking device.    Riser pipe reactor (1)    Regenerator (2)    Regeneration riser pipe (9)    Regenerated plug valve (10)    Vertical sleeve (25)