The leader-following consensus (LFCs) of nonlinear multi-agent systems (NMASs) with Markov switching topologies (MSTs) subjected to denial-of-service (DoS) attacks under event-triggered (ET) control is studied. An ET strategy is applied to reduce unnecessary signal transmission among agents, save network resources, and ensure systems performance. As a result of the open communication network among agents, it is inevitably subjected to attacks that leads to changing in the communication topologies. The communication topologies among agents are modeled as MSTs, and the transfer rates (TRs) are assumed to be partially unknown. DoS attacks are the most common attacks due to their destructive, stealthy, and easy implementation, so the network attacks considered in this paper are DoS attacks. Based on the distributed control theory and Lyapunov stability theory, the Lyapunov direct method and stochastic analysis method are used to explore sufficient conditions for the systems to achieve LFCs. Finally, an example is provided to verify the effectiveness of the methods and the correctness of the results.