High-precision strain sensing is pivotal for advancing Earth sciences, structural health monitoring, and biomimetic materials research, yet existing techniques face significant challenges in the simultaneously optimizing bandwidth, sensitivity, and noise floor. Conventional fiber sensors typically operate within narrow frequency bands (<1 kHz) or suffer from significant noise escalation beyond quasi-static regimes. To address this limitation, we introduce an optical frequency comb-based fiber-optic sensing system that enables ultrahigh-resolution strain measurement through advanced heterodyne beating techniques. Our system achieves the simultaneous broadband response (1 Hz–10 kHz) with unprecedented resolution performance, combining a dynamic strain resolution with a noise floor reaching ~1 fε/√Hz over much of the band with 5.25 pε static resolution. Furthermore, the temperature-compensated dual-FFPI (fiber Fabry-Perot interferometer) architecture maintains the high sensitivity throughout the entire frequency band, effectively overcoming the drift limitations of passive fiber sensors. This achievement enables femtoscale resolution strain measurement with flat noise characteristics, permitting the accurate detection of mechanical vibrations across diverse frequency regimes. Our work establishes a new standard for broadband high-resolution sensing, with transformative implications for next-generation geophysical monitoring networks, smart infrastructure systems, and integrated photonic sensing platforms.