The invention relates to a device and a method for continuously producing chlorinated paraffin-52. The device consists of a tubular reactor and a multi-stage complete mixing reactor which are in series connected, wherein the multi-stage complete mixing reactor is composed of a plurality of annular-space partition reactors which are connected in series; baffle plates between the adjacent annular-space partition reactors are sequentially lowered by the same height difference to form an overflow opening; each annular-space partition reactor is provided with a gas-phase charging hole, a gas-phase discharging hole, a liquid-phase forced circulating discharging hole, a liquid-phase forced circulating charging hole, a forced circulating heat exchanger and three ultraviolet-way light source sleeves which are uniformly distributed in the corresponding annular-space partition reactor. A liquid-phase chlorinated paraffin penetrates through the overflow opening to flow between the adjacent annular-space partition reactors, chlorine gas enters each annular-space partition reactor in a parallel form, a reaction tail gas enters the tubular reactor, and reaction heat is removed during circulation through the forced circulating heat exchanger. The device disclosed by the invention is compact in structure, capable of effectively controlling the reaction temperature, lowering the energy consumption and improving the device utilization rate and the product quality, and especially suitable for continuous production of the photocatalysis chlorinated paraffin.