A simple and reliable electrochemical sensor based on poly(DL-aspartic acid)-modified glassy carbon electrode was proposed for direct determination of brucine. The electrochemical character of brucine on this sensor was carefully and systematically studied by cyclic voltammetry. Some kinetic parameters were calculated and a reasonable reaction mechanism for brucine at the poly(DL-aspartic acid)/GCE was also proposed. Meanwhile, a new electroanalytical method for determination of brucine was proposed with a highly sensitive detection limit of 3 × 10−8 mol L−1 (S/N = 3) and a wide linear range of 5.0 × 10−8 to 9.0 × 10−5 mol L−1. More importantly, this sensor exhibited good stability and excellent reproducibility in the response for brucine.