The invention relates to a plane sliding bearing with the extremely low friction coefficient, and meanwhile discloses a preparing method of the plane sliding bearing. The plane sliding bearing with the extremely low friction coefficient comprises a bearing base body and a self-lubrication alloy layer, the bearing base body is steel, the self-lubrication alloy layer is manufactured with tin powder,nickel powder, copper powder, iron powder and graphite powder as raw materials, the thickness of the self-lubrication alloy layer is 0.5-3 mm, and gaps of the self-lubrication alloy layer are filledwith machine soil. The steel is A3 steel or 45# steel. The coating is formed through composite sintering of iron, nickel, tin, copper and graphite powder, and the strength, the pressure resisting capability and the corrosion resisting performance of the bearing are improved. After sintering, machine oil is sucked in a vacuum machine, the holes are full of lubricating oil, the self-lubrication performance is achieved, the friction losses are greatly reduced, and the friction coefficient reaches 0.025 or below and is superior to all usable solid materials in the nature.