Abstract The boiler superheater undergoes load cycling transients, once the thermal power plant participates in peak shaving. Thermodynamic optimization of a superheater is carried out by optimizing the flowrate/temperature matches between the hot and cold fluids during switching the load rate from 0.75 to 1.00. On the basis of a dynamic model of the superheater, the transient thermal performance is presented. Furthermore, the exergy delivery efficiency of the superheater was analyzed. The superheater outlet temperatures of hot fluid, metal wall, and cold fluid are highly affected when regulating work fluid inlet flowrates/temperatures. During switching the load transient, when increasing the hot fluid flowrate amplitude and variation rate by 50%, the average exergy efficiency (ηE,avg) of the superheater can improve by 1.04% and 0.13%, respectively. When increasing the cold fluid inlet temperature by 5%, ηE,avg can improve by 1.16%. When increasing the hot fluid inlet temperature by 5%, ηE,avg decreases by 0.74%. The exergy efficiency of the superheater is more sensitive to regulating temperature match than the flowrate match during switching the load transient process.