This study evaluates ground-motion (GM) acceleration conversion methods by applying them to strain-rate data from a horizontal Distributed Acoustic Sensing (DAS) array under both idealized and real-world conditions. We test four conversion methods—1) slant-stacking, 2) Lior’s method, 3) Lindsey’s method, and 4) Curvelet transform—through numerical modeling and by applying them to a publicly available 9 km horizontal DAS array dataset. Numerical simulations reveal critical calculation factors specific to each method and show that numerically derived apparent ground velocity can deviate from theoretical values when multiple elastic waves arrive simultaneously. In real-world applications, the slant-stacking and Lior’s methods are relatively insensitive to the measurement length of the straight DAS array. By contrast, the Curvelet method exhibits strong sensitivity to this factor, whereas Lindsey’s method shows weaker dependence. Implementing Lior’s method in the frequency-wavenumber domain also requires pre-determining water-levels by comparing adjacent seismograms. Additionally, we find that Lior’s method generates excessively high spectral levels above 13 Hz, which may lead to underestimation of the high-frequency spectral attenuation parameter (κ0), a key parameter in GM simulation. Collectively, these findings provide a technical guideline for the use of horizontal DAS arrays in future observational earthquake seismology.