Since Yuan and Ming Dynasties, the belief of Liu Mengjiang (刘猛将), the god of expelling locusts, has been formed in the South Yangtze River regions. There are many different records about the prototype of Liu Mengjiang, the god of expelling locusts. By combing the related literature, the author argues that Liu Mengjiang's prototype should be Liu Zai(刘宰) of Southern Song Dynasty. Liu Zai became the God of locusts, mainly because of his three large-scale relief hunger activities held in the golden altar, especially the first relief hunger activity in the second year of Jiading (嘉定) because of the famine by locusts. From this, Liu Zai was connected with expelling locusts. Liu Zai was widely worshiped after his death, he was seen as a sage by the scholars, but for the peasants, Liu Zai was their savior. Therefore, Liu Zai became the god of expelling locusts in the public sacrifice. However, the scholars and officials always tried to intervene and remould the image of locusts God in accordance with their own mainstream cultural logic, so that the original face of the god of expelling locusts became ambiguous.