[Background] Streptomyces venezuelae Snea253 is an actinomycete with nematicidal activity to plant-parasitic nematode. Bioinformatics analysis showed that γ-aminobutyrate transaminase gene (gabT) is one of the important genes involved in carbon metabolism in Snea253. [Objective] The purpose of this research is to clarify that the gabT gene affects the activity of the strain by regulating the γ-aminobutyric acid metabolic pathway of Snea253. [Methods] First, the mutant strain (Snea253-R) obtained by UV mutation was used to overexpress the gabT gene, and Meloidogyne incognita J2 was used as the target nematode. γ-aminobutyric acid and the metabolite succinic acid were detected by enzyme-linked immunoassay (ELISA) and high performance liquid chromatography (HPLC), and the nematicidal activity was also detected. Meanwhile, the gabT gene expression level, product content and nematicidal activity of wild-type strain with eight carbon sources culture were detected. [Results] The expression of gabT gene in overexpression strain R-pIB139 was up-regulated, γ-aminobutyric acid content was decreased, the content of succinic acid was increased, and the nematicidal activity was increased by 39% in comparison with the control. In eight carbon sources cultures, the carbon source medium with the higher relative expression of gabT gene in wild plants was soluble starch and corn starch. Under this condition, γ-aminobutyric acid content in fermentation broth was lower, the other products of metabolism were increased, and the nematicidal activity was higher. [Conclusion] By changing the expression of gabT gene, we confirmed that γ-aminobutyric acid shunt plays an important role in regulating the metabolism of Snea253 to enhance nematicidal activity.