Cardiac preload is the volume load of the heart. The flow of blood into the left ventricle is significantly increased during diastole, which may increase the burden on the heart in the long run, thus causing heart failure manifestations. Several types of diseases are common in clinical practice, such as mitral valve insufficiency, aortic valve insufficiency, and arteriovenous insufficiency, all of which can lead to an increase in left ventricular preload. Non-cardiac diseases such as hyperthyroidism and anemia can also cause an increase in the amount of blood returned to the heart, which can lead to an increase in cardiac preload. In the long term, the left ventricle will grow and enter the decompensated phase after compensatory growth. Patients will experience heart tiredness after activity, shortness of breath, chest tightness or even inability to lie down at night, and symptoms of left heart failure. Patients with excessive preload of the heart can be treated by medication or surgical intervention. In the case of valve-induced mitral valve closure insufficiency and aortic valve closure insufficiency, they can be solved by surgery of valve replacement; in the case of hyperthyroidism or anemia, patients should actively correct hyperthyroidism or actively correct anemia, i.e., correct secondary factors.