Schedulability test is an essential issue in real-time scheduling theory. Rate monotonic(RM) algorithm is one of the scheduling algorithms in real-time systems However, a general review on this field can hardly be seen. This paper presents a review of the various schedulability tests under RM algorithm, starting from the simplest ideal RM scheduling model and then going into the more complicated ones. Three subjects are covered: (1) schedulable tasks?CPU utilization least bound and the sufficient and necessary conditions; (2) condition of schedulable tasks taking the scheduling time cost into account; (3) condition of schedulable tasks taking priority inversion into account. Some appropriate examples are provided to illustrate and compare the relative merits among the discussed algorithms.