Optical coherence tomography angiography (OCTA) takes the flowing red blood cells (RBCs) as intrinsic contrast agents, enabling fast and three-dimensional visualization of vasculature perfusion down to capillary level, without a requirement of exogenous fluorescent injection. Various motion-contrast OCTA algorithms have been proposed to effectively extract dynamic blood flow from static tissues utilizing the different components of OCT signals (including amplitude, phase and complex) with various operations (such as differential, variance and decorrelation). Those algorithms promote the application of OCTA in both clinical diagnosis and scientific research. The purpose of this paper is to provide a systematical review of OCTA based on the inverse SNR and decorrelation features (ID-OCTA), mainly including the OCTA contrast origins, ID-OCTA imaging, quantification and applications.