In this paper, an event-triggered controller is designed for a class of stochastic systems subject to external attacks and unknown inputs. Concretely an event-triggered control strategy and its corresponding event-triggered transmission mechanism are presented based on a class of stochastic systems subject to external attacks and unknown inputs in the wireless transmission. Moreover, the transmission scheme on data of sensor is designed to determine when the transmission data can be sent. The controller gains that is designed derived by using the stochastic stability exponentially boundedness theory under the desired event-triggered condition. In addition, the corresponding event-triggered transmission strategy is derived in terms of an approximate quadratic performance index which gives a good balance among the control performance, the communication rates and the battery life of the node. A numerical example is given to verify the validity of the theoretical results in the simulation. The simulation results show that the estimator and event-triggered transmission strategy designed in this paper can balance the estimated accuracy and the number of transmissions well, which is of great significance for the energy saving of sensors.