This paper develops a new method to robust H_infin control problem for a class of uncertain switched systems by constructing single robust H_infin sliding surface. The method consists of two phases. One is to construct a single sliding surface which the reduced-order equivalent sliding motion is forced into, and to have the sliding motion robustly stabilized with H_infin disturbance attenuation level gamma under a hysteresis switching law to be designed; the other phase is to design variable structure controllers of the subsystems to thus drive the state of the switched system to reach the single sliding surface in finite time and remain on it thereafter. A numerical example is given to illustrate the effectiveness of the proposed method.