Abstract: Because of its outstanding inherent safety feature, high-temperature gas-cooled reactor (HTGR) is one of the most popular Generation Ⅳ nuclear energy system. However, the highly complex nonlinearity of HTGR-based nuclear steam supplying system (NSSS) puts higher requirements to its control system. On the other hand, T-S fuzzy control approach is a powerful tool in the control of complex nonlinear system, thus it is natural to consider applying this method on the control of the steam temperature of the HTGR-based NSSS. A T-S fuzzy steam temperature controller for the HTGR-based NSSS was first designed in this paper. Bilinear matrix inequalities were then constructed as stable conditions of the T-S fuzzy system based on the Lyapunov approach. A local minimization algorithm was finally used to solve the bilinear matrix inequalities for the parameters of the T-S fuzzy controller. The simulation results show that the designed T-S fuzzy controller does have a better performance than the traditional PI controller.