Abstract: Mismatch Negative (MMN) is a special electroencephalography (EEG) phenomenon that occurs when the brain is stimulated by external factors. MMN can objectively reflect the automatic processing of auditory information in the brain. Exploring the changes of MMN series in brain under multi-structure chords stimulation can help establish the mapping relationship between EEG signals and music, making it possible to generate chord music by using EEG signals. The Oddball paradigm was adopted in this paper, while MMN was obtained through one standard stimulus and three deviant stimuli. The major triad pattern consisting of a root with the notes in the group of small characters was regared as the standard stimulus, accounting for 70% of the stimulus sequence. Deviant stimuli were composed of minor triad, augment triad and major triad with an octave above the standard stimulus, accounting for 30%. The triggering factors of MMN was explored by examining the changes in multi-structure chords from standard stimulation to deviant stimulation. The impact of various stimulus attributes on MMN levels was studied through analysizing different deviant stimuli. The results indicate that MMN signals are generated in the jaw and central regions of the brain under chord stimulation. The changes in tonality and harmony of the strings could trigger the generation of MMN signals. Compared to chord attributes, pitch belonging to acoustic attributes has a higher impact on MMN levels. The MMN signals produced by men and women have significant differences, and women are more sensitive to chord stimuli. The results provide a basis for further exploring the response mechanism of the brain to music stimuli.