The test rig of low-temperature hot-water radiator is a typical multi-input multi-output (MIMO) thermal system with large time delay Aiming at the control of the supply air temperature and the temperature of the environmental chamber in the test rig the paper carries out the fuzzy control experiments and PI control experiments based on adjusting the electric heater in the supply air system in which there are two control loops with various delay time The experiments researched two types of fuzzy control methods which are the basic fuzzy control (BFC) and the self-organizing rules fuzzy control (SORFC) with zero initial control rules For the control loop of supply air temperature with short delay time PI control performs better with fast convergence speed and small overshoot than the BFC and the SORFC The convergence speed of the BFC method is lower than other two control methods For the control loop of chamber temperature with long delay time the SORFC has a satisfied control performance with less overshoot and stable error than the BFC and PI control (C) 2010 Elsevier B V All rights reserved