Summary: This article is concerned with exponential stability analysis for semi-Markovian switching systems subject to logarithmic quantization and bounded disturbances via sliding mode control. In order to design a sliding mode surface on quantized outputs, a state observer is utilized to generate the estimation of system states. Then a sliding mode controller is given to stabilize the resulting closed-loop semi-Markovian switching system. Furthermore, it is demonstrated that the proposed sliding mode controller can guarantee the reachability of the addressed sliding surface. Finally, based on cognitive radio communication system, a numerical example is performed to verify the effectiveness of the sliding mode control design technique.