The invention discloses a system for detecting the reliability of a converter valve cooling control device. The system comprises a detected device state signal monitoring device, a detected device control response monitoring device, a detected instrument sensor fault monitoring device, a detected key control element failure monitoring device, a central control and processing device, an industrial Ethernet communication device and a reliability detecting and analyzing background. Meanwhile, the invention further discloses a method for detecting the reliability through the system. The method includes the steps of collecting detection information, setting up a mathematic model, automatically calculating the concordance rate Cj, the speed rate Rk, the stability rate Sm and the availability rate Qn of detected redundant signals, and calculating the reliability Pi of the converter valve cooling control device according to the weight. The system has the advantages of being small in size and high in set-up speed, universality, reliability and the like, and safe and stable running of the converter valve cooling control device is ensured.