Abstract: To address the difficulty of characterizing dynamically evolving fracture parameters in tight sandstone reservoirs from conventional post-fracturing well testing, a mathematical model and interpretation method are developed using full-stage pressure data acquired during hydraulic fracturing operations. The proposed framework targets the coupled pressure response associated with fluid injection, fracture initiation, and fracture propagation in a single stage of a horizontal well. By introducing a half-fracture-length evolution coefficient, the time-dependent growth of fracture geometry is explicitly represented, and a variable-fracture-length flow model is formulated from mass conservation within the fracture system. An analytical expression for bottom-hole pressure is derived in Laplace space, and a quantitative interpretation workflow is established through Stehfest numerical inversion. In contrast to traditional approaches that rely primarily on shut-in pressure-decline data, the present method incorporates the entire pressure history of the fracturing treatment and provides an integrated computational framework for dynamic-fracture modeling, analytical solution, and parameter inversion. Sensitivity analysis indicates that the maximum fracture half-length and pumping rate dominate the bottom-hole pressure response, whereas the half-fracture-length evolution coefficient mainly controls the early-time pressure behavior after fracture initiation. Field application shows that the interpreted fracture half-length is 47.62 m, in close agreement with the field-estimated value of 44.5 m. The proposed method offers a practical tool for post-fracturing evaluation and treatment optimization in tight sandstone reservoirs.