Disclosed are a fluidized bed reaction and regeneration apparatus and a method for alkylating solid acid. The apparatus comprises an up-flow fluidized bed reactor, a liquid-solid separator, and a liquid-phase generator, which communicate in sequence. The bottom of the liquid-phase generator communicates with the bottom of the up-flow fluidized bed reactor, and a flow guiding pipe located at the bottom of the liquid-solid separator extends into the liquid-phase generator. Further, disclosed is a method for alkylating solid acid through the apparatus. In the liquid-phase generator, a dissolved-hydrogen regeneration liquid contacts a counter current of a deactivated catalyst for regeneration, so that the deactivated catalyst is efficiently regenerated. At the meanwhile, a regeneration medium is separated from a reaction product, so that fractionation cost is greatly reduced. The method for alkylating solid acid can be stably continuously operated; the selectivity of a target product is improved; and the economic benefit of apparatus operation is promoted.