The present invention relates to a method and a device for adjusting memory of a virtual machine. The method includes: checking memory usages of virtual machines according to a preset memory usage threshold to determine multiple virtual machines whose memory is to be adjusted; determining, according to parameters preselected by the multiple virtual machines whose memory is to be adjusted, priority levels of the virtual machines whose memory is to be adjusted; and adjusting, according to the priority levels of the virtual machines whose memory is to be adjusted, memory of the virtual machines whose memory is to be adjusted. According to embodiments of the present invention, memory of a virtual machine on which a key application or service is deployed is adjusted in time and prevents a process of a priority service from being affected due to delayed memory adjustment.