Perception of flood hazard risk and people's trust in the government have vital influences on risk communication. We conducted three studies to examine the relation and mechanism of trust and flood hazard risk perception. In Study 1, we found that people's risk perception and government trust were significantly negatively correlated. In Studies 2 and 3, using correlational and experimental methods, we found that the higher the public's trust in the government, the more they used heuristics to process risk information, and their risk perception was lower than the group with low trust in the government. Our results suggest that government trust can influence risk perception via heuristics.