This paper investigates the event-triggered observer design problem for nonlinear state affine systems. The output data of systems are event-triggered-sampled (sparse) and received by observer with certain time delays. A novel event-triggered mechanism is proposed to decide when the data need to be transmitted. The proposed observer globally and exponentially converges to the considered plant under the designed event-triggered mechanism. The effectiveness of the proposed event-triggered observer is illustrated with the comparison to existing works through simulations.