The invention provides a protection system applicable to small reactors. The system comprises a signal processing module, a logic processing module, an equipment interface module and shutdown circuitbreakers, wherein the signal processing module comprises a plurality of signal processing units, and each signal processing unit consists of a first diversity subunit and a second diversity subunit; the logic processing module comprises a plurality of logic processing units, and each logic processing unit consists of a third diversity subunit and a fourth diversity subunit; all the first diversitysubunits are connected with all the third diversity subunits, all the second diversity subunits are connected with all the fourth diversity subunits, and the third diversity subunits and the fourth diversity subunits of the same logic processing unit are connected with a pair of shutdown circuit breakers. The protection system solves the problems of low processing speed and large communication traffic in the prior art through separation of the signal processing module from the logic processing module.