The secondary cooperative control problem of an islanded microgrid through event-triggered mechanism is investigated in this paper. A distributed fixedtime secondary cooperative control strategy is proposed to obtain frequency and voltage magnitude secondary restoration, and also a proportional active power sharing under an undirected topology. We consider a centralized event-triggered mechanism to alleviate the communication burden and reduce the frequency of controllers update. Through this mechanism, the distributed fixed-time control protocols using frequency, voltage magnitude and active power sampling measurement values of distributed generations (DGs) only when the predefined event-triggered condition is satisfied. Compared with the conventional distributed asymptotic control protocols under period-triggered communication, the secondary control objectives of an islanded microgrid are achieved within a fixed settling time by applying the presented distributed fixed-time control approach, and the upper bound of settling time is unrelated to any initial states. Meanwhile, the presented centralized event-triggered communication method exhibits excellent performance in alleviating communication burden and promoting control efficiency. The theoretical proof is given by adopting Lyapunov method. The simulation studies are conducted to illustrate the effectiveness of the proposed control scheme.