Based on the Fishbein Behavior Intention Model, this article builds up an herd behavior intention for public health emergences in China, and conducts empirical analysis for selfhelp herd behavior and altruistic herd behavior under crisis through questionnaire survey for verification. This research is based on the theory of reasoned action, and revises it into the herd behavior intention model by adding the variable of informative social influence and increasing new links between variables according to related researches. And an empirical analysis has been done through questionnaires, taking an unknown influenza and donation in flood for examples. The empirical results show that the modified model has a good explanatory power. At the same time the empirical results also show that, informational social influence will take a leading role for the selfhelp herd behavior and vice versa the normative social influence dominant the altruistic herd behavior under emergency. In addition, the informational and normative social influences perform their affects in different ways in two in these different herd behaviors.