Recently, an increasing number of emergencies have taken place, agitating public panic. Under such background, we try to formulate a multi-agent based model to explore an effective information publication strategy to address such social problem in emergencies, from the perspective of government. In the proposed model, two main types of agents are included: citizens who determine their own status (panic or calm) based on the information from their friends and government, and government who determine when and which types of information (false but positive information, real but negative information, or response policy plan) to publish. Undoubtedly, the decisions of government will influence its credit ranking, and hence the attitude of citizen towards the published information. Taking the hazardous chemistry spill in the Songhua River of China as study sample, some interesting results can be obtained that releasing truth instead of false information and carrying out response measures quickly can efficiently relieve public panic.