This paper studies the consensus of general linear multi-agent systems with or without time delays. The observer-based event-triggered control schemes will be considered. For the conventional distributed consensus protocol, we will not update the relative state in continuous time, i.e., the relative state will be updated by some events which happened in discrete time. A completely decentralized event-trigger will be designed for multi-agent systems. It is shown that all agents can achieve consensus by the proposed protocol, if we design some appropriate feedback gain matrices. Numerical simulations are also provided and the results show highly consistent with the theoretical results.