Abstract: The spectral features in atrial septal defect （ASD） shunt was discussed in detail and the relation between these features and the pressure drop in two atrial was found out by comparing the corresponding data from ultrasonic pulsed Doppler examination and catheterization. Twenty patients with congenital ASD （male 13,female 7,age ranged 5-28 years,） were detected on ultrasonic pulsed Doppler echoca（?）diography with typical shunt spectrum and were comfirmed by intracardiac direct view surgery. The comparison between the shunt spectrum and the pressure gradient in the left and right atrium in 8 ASD patients indicated that spectral features of ASD shunt such as the flow shunt time,direction and phases of peak frequency shift etc.,mainly depended on the pressure gradient.It is concluded that ultrasonic pulsed Doppler spectr- al analysis provided a new,non-invasive method for the diagnosis of ASD.