Output voltage and frequency control in an islanded microgrid operation has high real-time performance requirements. Considering the impacts of load switching, communication topology switching, and other disturbances for an islanded microgrid, an improved microgrid distributed finite-time secondary control method with communication topology switching is proposed. This can realize finite-time output voltage and frequency regulation. First, by adding a tracking control error term with a power index 1 to the original finite-time control method, the finite-time voltage and frequency consensus algorithms are formulated, and corresponding stochastic closed-loop models are established respectively. Second, a Lyapunov analysis method is presented to verify the stability of the proposed method, and the finite-time upper bound expression is also derived. Finally, the effectiveness of the proposed control is verified by simulation experiments on Matlab/Simulink.