The invention provides a reaction system for preparing carbon fibers through cracking of hydrocarbon compounds, and a processing method and a use thereof. The reaction system comprises at least 3 series-connection two-dimensional fixed bed reactors, a material inlet of each two-dimensional fixed bed reactor is provided with an inlet three-way steering valve, and a material outlet of each two-dimensional fixed bed reactor is provided with an outlet three-way steering valve and a shut-off valve; a reaction material inlet pipeline of the reaction system is connected with an inlet of each two-dimensional fixed bed reactor through the inlet three-way steering valve, and a reaction material outlet pipeline of the reaction system is connected with an outlet of each two-dimensional fixed bed reactor through the outlet three-way steering valve; at least one two-dimensional fixed bed reactor of the two-dimensional fixed bed reactors is a standby reactor. The system and method realize intermittent catalytic carbon deposition continuous reaction by a reactor switching way, also can maintain stable high hydrocarbon compound decomposition rate, and are suitable for various carbon raw materials; and the process is sample.