The second-order consensus of multiple interacting non-identical agents with non-linear protocols is studied in this article. Firstly, it is shown that all agents with different non-linear dynamics can achieve consensus without a leader. Secondly, an explicit expression of the consensus value is analytically developed for the group of all agents. Thirdly, for the consensus of multiple agents with a leader, it is proved that each agent can track the position and velocity of the leader, which are different from those of the follower agents. Finally, numerical simulations are given to illustrate the theoretical results.