Event-based consensus problem of third-order nonlinear multi-agent systems is considered. Event-based controllers are proposed and MASs with event-based controllers are viewed as nonlinear systems with disturbances. By a degenerate transformation, an error system is derived from multi-agent systems, and consensus for multi-agent systems is converted into stability of the error system. Based on Lyapunov theory and Kronecker product method, several sufficient conditions on event-based consensus are obtained. It is shown that multi-agent systems can reach event-based consensus if the trigger parameter is sufficiently small and the control gain is sufficiently large under some simple conditions. Furthermore, the Zeno-behavior of the controllers is abstained. An example is presented to show the effectiveness of the derived results.