The invention discloses a sectional feeding alkylation reactor and an alkylation reaction method. The reactor comprises a reactor barrel, seal heads, a partition plate, an upper bed layer, a lower bed layer, a feeding pipe, a feeding distributing pipe, a rotary shaft, a supplementing material inlet, a discharging opening, a circulating cooling gas inlet, a circulating cooling gas refrigerating system and a circulating cool gas outlet. The invention further provides the alkylation reaction method. The method comprises the following steps: as the sectional feeding alkylation reactor is adopted, firstly forming an acidic hydrocarbon emulsion in the upper bed layer from iso-butane and concentrated sulfuric acid; and then carrying alkylation reaction on the acidic hydrocarbon emulsion and mixed hydrocarbon entering from the supplementing material inlet in a lower bed layer rotary bed. According to the alkylation method disclosed by the invention, by taking the concentrated sulfuric acid as a catalyst and the iso-butane and olefin as raw materials, the alkylation reaction is carried out. The alkylation reaction disclosed by the invention can be carried out at a low temperature, so that the reactor is low in acid consumption and small in equipment scale.