The optical coherence tomography (OCT) technology has been extensively used in clinical medicine, (including ophthalmology, intravascular endoscopy) and pharmacology, because of its non-invasive and non-contact features. Until now, OCT can be categorized into two major types according to the priority of imaging direction. One is the standard OCT which can perform A-line scanning along the incident direction of sample beam and has the ability to generate the longitudinal section (B scan) image, normally used to identify the individual retinal layers. The other is the en-face OCT (also called frontal section OCT) which can generate the transverse section image of sample layer in the direction perpendicular to the incident light. Using en-face OCT, the fine structure of the biological sample can be displayed in a field-of-view similar to that of the microscope, considerably extending the acquisition and representation modes of OCT imaging. Different signal acquisition methods can be adopted by en-face OCT systems. A detailed analysis and summary regarding these methods as well as the developing roadmap of en-face OCT are provided.