<p>The problem of fixed-time distributed optimization based formation control is discussed for multi-agent systems with external disturbances. To begin with, by introducing an integral sliding-mode strategy and two auxiliary functions with fixed-time convergence, a decentralized event-based intermittent control algorithm is developed to suppress the external perturbation. Subsequently, a gradient-based decentralized power-law control protocol is developed to guide each agent towards the minimum of its local cost function within a fixed time. Thirdly, a fixed-time distributed algorithm is presented and the formation is established in a fixed time around the minimum point of the global cost function. Finally, the proposed formation control scheme is demonstrated through several numerical analysis.</p>