The utility model discloses a passive emergency boronizing system for a nuclear power station, which comprises two boric acid storage tanks arranged in parallel, the two boric acid injection pipelinesare arranged in parallel, a plurality of first isolation valves are arranged on each boric acid injection pipeline, inlets of the boric acid injection pipelines are connected with outlets of the twoboric acid storage boxes respectively, outlets of the boric acid injection pipelines are connected with the reactor primary loop respectively, and the reactor primary loop comprises a reactor, a voltage stabilizer, a steam generator and a main pump which are sequentially connected through pipelines to form a loop; wherein the boric acid storage tank, the first isolation valve, the boric acid injection pipeline and the reactor primary loop are all arranged in the containment vessel. Compared with the prior art, the passive emergency boronizing system for the nuclear power plant is simple in structure and safe to use, and when an accident occurs in the nuclear power plant, boric acid can be rapidly injected into a primary loop of a reactor to keep the subcritical state of the reactor.