This paper introduces several types of communication between SW MODEM and the serial port of computers which are applied to a semiduplex SW transmitter - receiver , analyses the realization of communication between SW MODEM and computer serial port , and goes into particulars several key techniques of the communication programme.As shown by experiment results: working out the communication procedures between SW MODEM and computer serial port can realize datatransmission in factual channel. This proves the availability of communication programme between SW MODEM and computer serial port based on thread event- driven style.