To further improve the efficiency of short-chain fatty acid (SCFAs) production by alkaline anaerobic fermentation, sludge was pretreated using a series of copper ion with gradient concentration (0, 10, 25, 50, 75, 100 mg/L). The optimal concentration of copper ion was determined by the cell decay rate of sludge and the concentration of released organic matter. Then the effect of copper ion pretreatment on the production of SCFAs by alkaline anaerobic fermentation of sludge was investigated with the optimal concentration. The results showed that the cell decay rate achieved by 50.9% when the concentration of copper ion was 100 mg/L. When the concentration of copper ion was 25mg/L and the sludge was pretreated for 24h, the increase ratio of substrate required for acid production was a maximum of 0.08mg/mg?h. Based on the efficiency, 25mg/L was the optimal concentration of copper ion. The sludge pretreated with 25mg/L copper ion was directly subjected to alkaline anaerobic fermentation, and the maximum amount of SCFAs production reached 791.6mg /L on the 6th day, which was 370.1mg /L higher than that of the untreated sludge.