The invention provides a testing system for studying a dead tube section phenomenon of a nuclear power plant. The testing system comprises a dead tube section and a first mechanism, wherein the first mechanism is used for simulating internal temperature of the dead tube section; the dead tube section is a completely sealed metal pipeline; a liquid inlet and a liquid outlet are formed in the dead tube section; the first mechanism comprises a convection tube, a heater, far heat transfer electrical resistance thermometers, magnetic turnover plate liquidometers and a first far heat transfer differential pressure transmitter; the convection tube is a completely sealed metal pipeline and forms a communicated first loop with the dead tube section through two pipelines; an exhaust hole is formed in the convection tube; the heater is connected with the dead tube section to achieve liquid heating treatment; a plurality of far heat transfer electrical resistance thermometers are respectively mounted on the dead tube section and the convection tube; one of two magnetic turnover plate liquidometers is mounted on the dead tube section; the other one of the two magnetic turnover plate liquidometers is mounted on the convection tube; and the first far heat transfer differential pressure transmitter is mounted on the dead tube section and is serially connected with the dead tube section to form a second loop. By adopting the testing system, the dead tube section phenomenon can be studied and discussed by using testing simulation technical measures, and in addition the testing system is reasonable and reliable in design.