The rapid development of electrical skin and wearable electronics raises the requirement of stretchable strain sensors. In this study, an active fiber-based strain sensor (AFSS) is fabricated by coiling a fiber-based generator around a stretchable silicone fiber. The AFSS shows the sensitive and stable performance and has the ability to detect the strain up to 25%, which is also demonstrated to detect finger motion states. It may play an essential role in future self-powered sensor system.