Polyquaternary ammonium salt as well as preparation method and application thereof

The invention discloses polyquaternium and a preparation method and application thereof, and belongs to the technical field of electroplating. The polyquaternary ammonium salt comprises a plurality of repetitive units, each repetitive unit comprises a diester group and a biquaternary ammonium salt group which are connected, and the diester group comprises a linking group and two ester groups; the linking group is alkyl, aryl, aralkyl, alkyl containing an ether bond, aryl containing an ether bond or aralkyl containing an ether bond, two end groups of the linking group are respectively connected with oxygen groups of the two ester groups, and R groups of the two ester groups are connected with N atoms of corresponding biquaternary ammonium salt groups; the biquaternary ammonium salt group is obtained based on a bis-tertiary amine compound. The leveling agent based on the polyquaternium is beneficial for obtaining a plating layer with high coplanarity, the operation window of the leveling agent based on the poly