This paper summarizes the development and verification of the tether deployment and towing mechanism in the space debris removal missions that have been carried out. Based on the low-tension towing strategy and taking into account safety and stability requirements, it puts forward the capability requirements of high-accuracy tether length and tension measurements. Focusing on a towing mechanism that uses a collaborative approach to tether retraction-release and storage, and taking into account the effects of on-orbit conditions, this article proposes a method for high-accuracy measurement and calibration of tether length and tension. By adjusting the calculation coefficients based on actual measurements, the absolute error in tether length calculation within the storage module’s in a long retract/release distance is minimized. When the discrepancy between the length calculations of storage module and retraction-release module exceeds the set threshold, the length calculated by storage module is injected into retraction-release module, achieving precise correction of tether length for long retract/release distance. Comprehensive calibration methods, including initial calibration, zeroing time drift before use, and temperature compensation calculation, are proposed to enhance the precision of tension measurement for the towing mechanism. The test results confirmed the efficacy of the method for measuring and calibrating tether length and tension of towing mechanism. This paper combines the characteristics of the towing mechanism with real-world usage conditions. It conducts research on measurement and calibration methods, along with ground test verification, demonstrating strong engineering feasibility.