The effects of different concentrations of γ-aminobutyric acid （GABA） on the growth，root morphology，and mineral nutrient uptake of trifoliate orange ［Poncirus trifoliata （L.） Raf.］ seedlings were studied to identify the regulatory effects of exogenous GABA on the growth and mineral nutrient uptake of trifoliate orange seedlings.A nutrient solution hydroponic culture was conducted with a control and five concentration gradients of GABA including G1 （0.01 mmol/L），G2 （0.05 mmol/L），G3 （0.1 mmol/L），G4 （0.5 mmol/L），and G5 （1 mmol/L）.The plant height，biomass，root morphology and the content of mineral elements in trifoliate orange seedlings were measured after 30 days of treatment.The results showed that low concentrations of GABA including 0.01 mmol/L，0.05 mmol/L，and 0.1 mmol/L had no significant effect on the plant height，total root length，and biomass accumulation of trifoliate orange seedlings，but significantly changed the root morphology，increased the root surface area，and the root volume.High concentrations of GABA including 0.5 mmol/L and 1 mmol/L inhibited the growth and root development of trifoliate orange seedlings.When the concentration of GABA reached 0.5 mmol/L，it significantly reduced the total root length，main root length，and lateral root length.When the concentration reached 1 mmol/L，it further inhibited the accumulation of plant height and biomass，and significantly reduced the root surface area.Low concentration of GABA promoted the content of N，P，Ca，B，and Mo in the roots of trifoliate orange seedlings，increased the content of K in the stems and the content of P in the leaves，and increased the accumulation of N，P，K，and Mo per plant.However，high concentrations of GABA reduced the content of mineral elements （excluding N） in various organs of trifoliate orange seedlings，and inhibited the nutrient accumulation of trifoliate orange seedlings.It is indicated that the effects of exogenous GABA on the root growth and mineral nutrient absorption of trifoliate orange seedlings had a trend of promoting at low concentrations and inhibiting at high concentrations.The appropriate concentration of GABA can promote the root development of trifoliate orange seedlings，increase the root nutrient absorption area，and facilitate the accumulation and upward transportation of mineral elements.The optimal concentration is 0.05 mmol/L-0.1 mmol/L.When the concentration is too high，it hinders the normal growth and mineral element absorption of trifoliate orange seedlings.It will provide a theoretical reference for the practical application of GABA in enhancing the growth of citrus seedlings.