Objective To explore the role of SLIT-ROBO Rho GTPase-activating protein 2 (srGAP2) in spinal motor neuron degeneration in amyotrophic lateral sclerosis (ALS).   Methods   Applied bioinformatics analysis to investigate the expression changes of srGAP2 in the spinal cord of human superoxide dismutase 1(hSOD1) mutant ALS transgenic mice. hSOD1G93A mutant ALS transgenic mice were selected for animal experimental validation, with littermate wild type(WT) mice serving as the control group. A total of 36 pairs were divided into four groups, namely the pre-onset stage, early-onset stage, mid-onset stage, and late-onset stage. The expression changes and cellular localization of srGAP2 in the spinal cord of ALS mice were detected by Real-time PCR, Western blotting and immunofluorescent double-label staining. The hSOD1G93A mutant NSC34 motor neuron-like cell model was established, and in vitro experiments were carried out to detect the changes in srGAP2 expression, and the effects of srGAP2 over-expression on the viability of hSOD1G93A mutant NSC34 cells and the growth of cell protrusions.   Results  Bioinformatics analysis revealed abnormally low expression of srGAP2 in the spinal cord of hSOD1 mutant ALS  mice. Animal experiments verified that compared with the WT mice, the expression of srGAP2 was reduced at both mRNA level and protein level in the spinal cord of hSOD1G93A mutant ALS transgenic mice at early-onset, mid-onset and late-onset stages. Compared with the WT mice, srGAP2 integral absorbance (IA) values in srGAP2⁺/NeuN⁺ double-positive cells in the anterior horn of the spinal cord of hSOD1G93A mutant ALS transgenic mice were lower, srGAP2 IA values in srGAP2⁺/GFAP⁺ double-positive cells were higher; Compared with the hSOD1WT NSC34 cells, the expression of srGAP2 was reduced at both mRNA level and protein level in hSOD1G93A mutant NSC34 cells. Over-expression of srGAP2 elevated the viability of hSOD1G93A mutant NSC34 cells, and up-regulated the expression level of synapse-related protein βⅢ-tubulin and growth associated protein 43（GAP43）.   Conclusion   Low expression of srGAP2 is closely associated with the progression of ALS, while over-expression of srGAP2 can promote outgrowth of cell protrusions and exert a protective effect on spinal motor neurons in ALS.