Abstract: OBJECTIVE To optimize the extraction process for alkaloid by the central composite design-response surface methodology from Solanum nigrum. METHODS On the basis of one factor tests, the method of the central composite design-response surface analysis 3 factors including concentration of methanol in the extraction impregnate, extraction temperature, time, and extraction percentage of alkaloid from Solanum nigrum as response value was adopted. RESULTS The quantitative relationships between 3 factors and the response value were characterized by DPS. Optimal formulation was proposed to concentration of methanol 73.6%, extraction temperature 60 ℃, extraction time 63.3 min. The predicted value and measured value of alkaloid from Solanum nigrum was 0.683 0 mg·g^-1 and 0.676 3 mg·g^-1, respectively. CONCLUSION The result indicates that extraction process of alkaloid from Solanum nigrum could be achieved by the central composite design-response surface methodology, and it is predictable.