Abstract: A kind of timbre model based on sad-type instrument is presented，which can provide the sound basis for emotion-based algorithmic composition.Musical sound samples of the instrument are collected.This instrument is good at expressing sad emotions.And spectral and envelope characteristics are obtained by discrete Fourier transform and analysis calculation method of the instrument waveform.Finally，a kind of timbre model based on sad-type instrument is constructed.Experimental results show the sad-type sound generated by the model and the model itself are well regulated.Compared with the traditional form of recording，this method is of low cost，flexibility，and also plays an important role in promoting the development of computer music technology and the emotional arithmetic composition.