This study was conducted to investigate the effects of different levels of γ-amino butyric acid (GABA) from 0 to 150 mg/kg on the performance and serum hormone levels in Yorkshire lactating sows. Forty sows were randomly allocated to five treatments with eight replicates in each and one sow in each replicate according to single factor design. The trial lasted for 21 days. The results showed that 1) the GABA had a positive effect on improving feed intake, weight loss, estrus interval and performance of piglets to some extent. The effect of GABA was mainly influenced by the level of GABA added in diet and nursery phase. It was noted that the effect of GABA in lower levels was better than that of high levels and became even better with the nursery phase prolonged. As to feed intake, the effect of 50 mg/kg GABA was better than that of the control in week 1 （P<0.01）, week 2 （P<0.10）, week 3 （P<0.10） and the whole experimental period （P<0.01）; 2) comparing with the control group, the level of leptin in serum in 50 mg/kg GABA group significantly decreased （P<0.05）, and the level of NPY obviously increased in week 2 and week 3 （P<0.01, P<0.05）. In addition, the level of GH in 50 mg/kg GABA group in delivery （P<0.10） and week 2 （P<0.05） were obviously higher than that of the control group. In conclusion, GABA improved the performance and feed intake by regulating the levels of NPY and leptin in serum of sows, and the effect was mainly related to the addition level and nursery phase. The suitable GABA level was 50 mg/kg.