The invention provides a potassium ion battery negative electrode active material, a potassium ion battery negative electrode material, a potassium ion battery negative electrode, a potassium ion battery and an application thereof, belonging to the technical field of potassium ion batteries. The potassium ion battery negative electrode active material provided by the invention comprises a ruthenium pentoxide composite material, wherein the ruthenium pentoxide composite material comprises a ruthenium pentoxide composite material containing a doping ions and / or a coating layer. The ruthenium pentoxide composite material has excellent potassium ion transport channels, can realize rapid insertion and de-intercalation of potassium ions, has stable crystal structure, adopts the reaction mechanism of intercalation and pseudocapacitance dual mechanism, prepares the potassium ion battery with the advantages of long cycle life, high specific capacity and low cost, can solve the problem of priceincrease caused by insufficient lithium resources, avoids the problems of expansion and pulverization of the alloy-type negative electrode of the potassium ion battery, slow dynamics of the intercalated carbon material and the like, and can be widely applied to electric tools, electronic equipment, electric vehicles or energy storage equipment.