Abstract: Timbre and flexibility are two significant indexes of synthesis，in order to combine both of their features，based on methods of FM synthesis and sampling intervals synthesis，to realize a new method of digital-synthesis by time-domain waveform envelope processing and frequency-domain modulation to a key period waveform taking from guitar.The results of synthesis can sound better performance，also have a certain flexibility in design and application.It is achieved the designing in computer via MATLAB，provides a reference to the designing of digital synthesizer for portable and small equipment.