This study attempts to address the mobilizing emotions in social movement protests through an exploration of the case of the 2014 Hong Kong Umbrella Movement. Through methods of non-participant observation and in-depth interviews, Yang’s emotional achievement theory and Jasper’s perspective of reciprocal emotions and shared emotions are examined in the research. In the paper, protesters’ emotional dynamics are analyzed in the four main stages of the Umbrella Movement: the initial emotional mobilization on new media, the high tide of emotional overflow, the deadlocked stage, and an embarrassed ending with despair and expectations, which reveal the four main features of protesters’ emotional mobilization in the Umbrella Movement. Following Yang’s theory of emotional achievement, the author finds that the four features of protesters’ emotional mobilization in the Umbrella Movement are that it is situational, interactional, temporal, and integral to identity. In addition, it was fascinating for the author to observe an interesting phenomenon that goes against Jasper’s description about protesters’ reciprocal emotions; in the 2014 Hong Kong Umbrella Movement, reciprocal emotions are not only the affective ties of positive relationships among protesters, but also have a negative influence on the relationships between protesters, and also do harm to the solidarity of protesters if the reciprocal emotions are passive. Last but not least, the shared emotions of protesters in the Umbrella Movement exert a positive impact on the solidarity and communication among them.