The purpose of this study was to determine the intervention effect of metformin on rats with acute gout and the influence of serum free fatty acids (FFAs). Twenty-one Wistar rats were randomly divided into the 200 mg/kg metformin group, 300 mg/kg metformin group, and control group. After five days of administration, sodium urate crystals were injected into the metatarpal joints of the rats to establish the model. The volume change of the metatarpal joints of the rats was measured and we used a biochemical sensor to determine the FFA concentration in serum. Metformin administered at 300 mg/kg body weight showed good anti-inflammatory and anti-swelling effects within 24 h after modeling, and reduced the swelling rate of the ankle joint. Compared with the control group, the ankle swelling rate of the 300 mg/kg metformin group decreased 36 h after modeling and was lower than that of the 200 mg/kg metformin group 36, 72, and 96 h after modeling (P < 0.05). The serum FFA concentration in the 300 mg/kg metformin group significantly decreased compared with that in the control group, and the difference was statistically significant (P < 0.05). In conclusion, 300 mg/kg metformin can inhibit the joint swelling of rats with acute gouty arthritis, and the effect is better than that of 200 mg/kg metformin. The possible mechanism of metformin in the treatment of acute gouty arthritis in rats is as follows: by reducing the FFA concentration in serum, metformin interferes with the acute attack of gouty arthritis. A possible mechanism of the effect of metformin in treating acute gouty arthritis in rats is the intervention of the acute onset of gouty arthritis by inhibiting the increase in serum FFA concentration.