The fiber optic gyro (FOG), which is currently one of the most widely used fiber optic sensors, has firmly occupied a considerable market share of inertial sensors and offers the benefits of high stability and easy integration. The resonant FOG, also known as the RFOG, is a sensor that identifies a rotation rate by employing the use of a fiber ring resonator. It possesses a higher application potential in terms of optical stability and system miniaturization because it is an FOG of the second generation. This review begins with an exploration of the RFOG principle and then moves on to concentrate on the two aspects of RFOG optical noises suppression and signal processing in order to examine the progression of RFOG in the most recent years. Several distinct types of RFOG schemes that have a high application potential are dissected individually; these are the types of schemes that are anticipated to become mainstream application schemes in the not-too-distant future. In the end, the prospect and research challenge of RFOG are presented to help researchers clarify research directions. This article presents an in-depth analysis of the current state of research regarding RFOG-related technologies and offers a forecast regarding the path that the inertial sensor will take in the foreseeable future.