The diagnosis of atrial septal defects can be established by ultrasound and color Doppler. The main points of ultrasound diagnosis are as follows: firstly, direct signs of atrial septal echogenicity can be seen in two-dimensional ultrasound, and indirect signs can be seen in right atrial and ventricular enlargement and mild widening of the pulmonary arteries under ultrasound. Color Doppler can show the direction of the blood flow beam, and can measure the shunt beam of the left and right atria, and indirectly measure the location and diameter of the atrial septal defect according to the flow beam. For special types of atrial septal defects, such as the primary foramen ovale type, the defect is seen to be located at the lower end of the atrial septum. In patients with atypical atrial septal defects or in combination with other malformations, the diagnosis should sometimes be confirmed by cardiac catheterization.