The fault detection problem is investigated for a class of networked systems with sensor saturation and communication constraint. A novel event-triggered mechanism is introduced to save limited network resource in the sensor-to-filter channel. After properly augmenting the states of the original system and the fault detection filter, the addressed fault detection problem is converted into an auxiliary filtering problem. By utilizing Lyapunov stability theory and free-weighting matrix technique, the sufficient conditions for the existence of the fault detection filter is established in terms of linear matrix inequalities, and the corresponding optimal filter parameters can be easily derived by solving a convex optimization problem via a semi-definite program method. Finally, a numerical example is provided to illustrate the validity of the event-triggered fault detection scheme.