Abstract: Based on the theories of the sliding mode control, the compensators and the fuzzy logic control, this paper presents a new fuzzy sliding mode control method with a fixed-order compensator for application to seismically excited building structures with an active tuned mass damper (ATMD). Considering that actuators are always of limited capacity in practice, this paper designs the saturated control law to be used when the needed control force exceeds the maximum control force of an actuator. The major advantages of this method over the conventional sliding mode control method via exponential reaching law are as follows: (i) it makes trade-offs between control efforts and specific response quantities of the structure through the use of linear quadratic optimal control theory, (ii) it can keep the chattering effect sufficiently low through the use of a new fuzzy reaching law. Finally this paper gives numerical simulations for SDOF (Single-Degree-of-Freedom) shear building model with ATMD. The simulation results obtained from the proposed control scheme are compared with those obtained from ATMD system excluding the compensator, the tuned mass damper (TMD) system and active mass damper (AMD) system, which shows preliminarily that the new control method is quite effective.