The consensus protocol with respect to time-varying jointly-connected topologies entitles multi-agent systems reach consensus under the circumstance with unstable communication. Additionally the protocol ensuring finite-time convergence benefits multi-agent systems in engineering practicability because the cooperative pattern is achievable in finite time. For homogeneous agents without predetermined leaders, this paper provides a decentralized finite-time consensus protocol. The proof based on LaSalle's invariance principle verified that, the protocol makes second-order agents asymptotically converge to an average consensus within finite time, even if the interaction topology among them is time-varying but stepwise jointly-connected. Finally the simulation compares the dynamics characteristics between systems with jointly-connected and disjoint-connected topologies.