Abstract <p>In this paper, the molecular dynamics method was used to investigate the size dependency of mechanical properties and fracture behavior in GaAs nanowires. Density Functional Theory (DFT) was employed to study the bandgap, carrier effective mass, mobility, and relaxation time of 〈011〉- and 〈111〉-oriented GaAs nanowires. The results revealed that the orientation, diameter, and wall thickness of the nanowires had a significant impact on their mechanical properties, whereas the length and cross-sectional shape exerted a relatively minor influence. Following fracture, the nanowires exhibited a partial self-healing phenomenon, characterized by limited lattice recovery and the formation of a stable new lattice structure with a bond length of 2.55 nm. The 〈001〉-oriented nanowires were found to be unsuitable for practical applications. In contrast, 〈111〉- and 〈011〉-oriented nanowires are suitable for different response wavelengths, with 〈111〉-oriented nanowires demonstrating superior mechanical properties, greater structural stability, and minimal lattice distortion, while 〈011〉-oriented nanowires exhibited better electron transport characteristics.</p>