The invention provides a rotary welding positioning device of a lithium ion cylindrical battery cover plate. The rotary welding positioning device comprises a base, and a front clamping piece, a positioning assembly and a rear clamping piece are fixedly arranged on the central axis of the base in sequence, wherein the positioning assembly comprises an outer cylinder, at least two positioning plates are arranged inside the outer cylinder along the axial direction of the outer cylinder, and the back face of the positioning plate is fixedly connected with a cylinder wall of the outer cylinder through a spring; the positioning plate comprises a positioning plate body which the front surface is in an inwards-concave shape, the two ends of the positioning plate body are correspondingly connectedwith arc-shaped end plates extending towards the cylinder wall direction of the outer cylinder, and all the end plates are located outside the outer cylinder to form an outer trumpet shape; and a fixing part is fixedly arranged at the inner concave part of the positioning plate body, the fixing part comprises a hoop and a connecting rod, and freely-rotating balls are sleeved with the hoop. According to the device, the cylindrical battery with different diameters can be positioned in a floating mode, the rotating center of the cylindrical battery can be accurately positioned, so that the welding quality is improved; and a laser welding area is provided with a welding dust removal interface, so that the environmental pollution is reduced.