This paper explores the active fault tolerant control issue for a class of uncertain nonlinear systems using a control allocation (CA)-based integral sliding mode control (ISMC) technique. When the information of fault detection and diagnosis is available, the presented scheme can tolerate some of the actuators' faults, while maintains the main advantages of both CA and ISMC techniques. A remarkable one is that, when the uncertainties and/or disturbances are matched, the state trajectories of the selected nominal system and the uncertain faulty system are identical. As a result, engineers can predictively address the performance of matched uncertain faulty system in accordance with the performance of a selected nominal system. The proposed analytic results are applied to the attitude control of a spacecraft to demonstrate the benefits of the proposed scheme.