The invention discloses a software test system and method for a digital reactor protection system of a nuclear power plant. The system includes a probability distribution assembly, a parameter generation assembly and a data analysis assembly; the probability distribution assembly is used for conducting probability distribution on multiple selection modules of a parameter generation module and conducting probability distribution on the next branch selection step of each selection module; the parameter generation assembly includes the selection modules, and is connected with a part of the probability distribution assembly and used for generating the expectation value and the operation parameter value of each round of test; the data analysis assembly is connected with the parameter generation assembly, used for conducting analysis and comparison on the expectation value and the operation parameter value of each round of test, and the test results of multiple rounds of tests are counted up and led out in a user-defined mode. The provided software test system and method for the digital reactor protection system of the nuclear power plant have the random characteristics of an operational profile, comprehensively covers the range of parameters, and makes the operation state of the nuclear power plant fully simulated in a test environment.