Recent development in health monitoring applications have heightened the need for wearable devices to acquire human bio-electrical and bio-chemical signals. It is urgent to develop highly customizable analog front-ends that meet diverse processing and performance requirements such as low cost manufacturing, unique form factor for flexibility, and accurate acquisition of signal under strict power constraint. Organic thin-film transistor (OTFT), owning superior mechanical flexibility and feasibility of being manufactured on arbitrary plastics, is regarded as a promising technology platform for developing such customized front-ends. This paper gives a brief overview of the recent development of OTFT-based analog front-ends. The flexible low-voltage device technology is firstly discussed. Efforts devoted to OTFT-based analog front-end circuits and system are then introduced. Finally, the remaining challenges for advanced OTFT front-ends are clarified. This review will provide guidelines for processing and design of flexible OTFT analog front-end for wearable electronics.