<p>Drought-induced desiccation cracking can trigger several weakening mechanisms in surface soils, potentially precipitating instability and failure of slopes and earthen structures. To investigate the potential application of distributed fibre optical sensing (DFOS) based on optical frequency domain reflectometry (OFDR) technology in characterizing the two-dimensional (2D) desiccation cracking processes of surface soils, a comprehensive test device is utilized to conduct soil evaporation tests, continuously record water content changes, desiccation cracking evolution, and FO sensing strain status. A deep learning-based quantitative analysis method is employed to meticulously examine the relationship between 2D cracking geometric parameters and strain status. The comprehensive analysis not only reveals the mutual feedback response mechanism between the strain status and the soil evaporation-shrinkage-cracking processes, but also clarifies the early detection distance of OFDR technology for 2D desiccation cracking. Specifically, OFDR technology can detect the propagation of horizontal desiccation cracks up to 23 mm in advance with a strain measurement accuracy of 1 µε. To address the spatial continuity issue in OFDR sensing strain data, an innovative high-resolution characterization framework is proposed by combining the finite element method (FEM) and OFDR technology, referred to as the FEM-OFDR framework. Comparative results indicate that the proposed FEM significantly surpasses both the kriging and radial basis function (RBF) methods in inferring missing OFDR sensing strain data. Notably, during the drying process, reaching a critical water content causes the local decoupling between the uncracked clods and the substrate, resulting in a decreasing trend in the sensing strain at the crack position. This study provides crucial technical means and theoretical support for a deeper understanding of the mechanisms driving 2D desiccation-induced shrinkage and cracking in surface soils.</p>