The ECG and lead lines are divided into 5 colors: red, yellow, green, black, and white, and white is divided into C1, C2, C3, C4, C5, and C6 for a total of 10 leads. Red is connected to the right upper limb, yellow to the left upper limb, green to the left lower limb, black to the right lower limb, and white leads are connected to the corresponding leads in the chest. Specific placement is as follows: 1. Limb leads: Limb lead Ⅰ is connected to the negative pole in the right upper limb and the positive pole in the left upper limb. Limb lead II is connected to the negative pole in the right upper limb and the positive pole in the left lower limb. Limb lead III is connected to the negative pole in the left upper extremity and the positive pole in the left lower extremity. Pressurized unipolar limb lead aVR, connected in the right upper limb is positive, and the left upper limb and left lower limb are connected together is negative. Pressurized unipolar limb lead aVL, connected in the left upper limb is positive, and the right upper limb and left lower limb are connected together is negative. Pressurized unipolar limb lead aVF, the left lower limb is connected to the positive pole, and the left upper limb and right upper limb are jointly connected to the negative pole; 2. Thoracic lead: V1 it is placed at the 4th gap of the right edge of the sternum; V2 is at the 4th rib gap of the left edge of the sternum, opposite to V1; V3 is at the midpoint of the line connecting V2 and V4; V4 is at the midline of the left 5th intercostal clavicle, which is under the nipple; V5 is the left anterior axillary line and V4 at the same level; V6 is the left mid-axillary line at the same level as V4 and V5; V7 is at the left post-axillary line at the same level as V4 and V5; V8 is at the left subscapular angle at the same level as V4, V5, V6, and V7; V9 is at the left paraclinoid at the same level as V4, V5, and V6; V3R, V4R, and V5R are on the right side of the chest at the corresponding parts of V3, V4, and V5, one on the left , one on the right.