The invention provides an auxiliary piano composition system and method based on user demonstration audio style. The system herein comprises an audio processing module, a note sequence mapping module,a neural network module and an intelligent device. The audio processing module is used for extracting note features of an audio file; the note sequence mapping module is used for performing mutual mapping translation between the note features of the audio file and input and output values of a neural network; the neural network module is used for training a network model to obtain a prediction model to assist a user in assisted composition or full-automatic composition; the intelligent device is a human-machine interactive device for providing a user with the functions of uploading demonstrative audio, inputting a note sequence and trying and predicting a generated note effect. The system herein meets a user's personal needs, can generate piano music of the style that the user favors, canbring creative inspiration for the professional, and can assist users with no music basis in participating in music production, thereby improving entertainment of music.