Optical frequency domain reflectometry (OFDR), celebrated for its exceptional sensitivity and distributed strain sensing capabilities, has demonstrated significant application potential in critical domains such as aerospace and structural health monitoring. However, current OFDR-based strain sensing technologies encounter a critical challenge: position resolution degradation caused by positional mismatches, which impedes the simultaneous achievement of high resolution, broad measurement range, and high-precision measurement. To address this issue, this paper introduces a novel distributed strain sensing technology with an extended dynamic range, which integrates a position self-correction algorithm and non-uniform Gaussian image filtering. An OFDR-based distributed strain sensing system is constructed to validate the effectiveness of these two algorithms. Experimental results show that the proposed method can accurately measure strains up to 8000 με with a spatial resolution of 4 mm over a 5.4 m optical fiber. Compared with conventional approaches, this method significantly expands the strain measurement range, enhances measurement accuracy, and achieves a synergistic optimization between high resolution and large measurement range. These improvements provide a robust solution for deploying OFDR systems in complex strain monitoring scenarios.