Integrating sweat biosensors into daily wear has the potential to effectively monitor personal lactate levels, offering the advantages of convenience, precision, and multi-point detection. However, existing wearable fabric sweat biosensors have limitations in terms of long-term repeatable detection and washability due to the difficulty of building a stable layer of recognition materials on the highly curved fiber surface. Here, a long-term repeatable and washable electrochemical fabric biosensor is reported based on a fiber electrode with multi-scaled aligned channels for efficient and reliable lactate detection. Through the functionalization of a molecularly imprinted polymer with redox-sensitive nano reporters, the fabric biosensor exhibits impressive in situ long-term repeatable detection for more than 400 times, washability, and stability under deformations. The multi-scaled channels contribute to a desired electric field distribution and thus a reliable interface between the polymer and the fiber. Employing industrial sewing technology, a 20 m (L)  ×  0.5 m (W) sensing fabric is further produced. Ultimately, combined with a wireless communication element, the fabric biosensing system can immediately track lactate levels.