Consensus problem of second-order multi-agent systems with velocity damping term in agent's dynamics is investigated. Based on frequency-domain analysis, decentralized consensus condition, which depends on the input delays, is obtained for the system based on undirected and symmetric graph with heterogeneous input delays. For the system based on directed graph with both heterogeneous input delays and communication delays, decentralized consensus condition, which is dependent on the input delays but independent on the communication delays, is also obtained. Simulations illustrate the correctness of the results.