The invention relates to the field of laser welding auxiliary equipment, in particular to a positioning device of a high-precision laser butt welding machine. The positioning device comprises a base,a power mechanism, two butt joint mechanisms and two positioning mechanisms which are symmetrically arranged on the top of the base and have the same structures. The two butt joint mechanisms are symmetrically arranged between the two positioning mechanisms. Each positioning mechanism comprises a guide seat, a positioning clamp, an intercepting part and a pressing part. The positioning clamps canbe movably arranged above the guide seats through tension springs, the two intercepting parts are arranged at the close ends of the two positioning clamps, the intercepting parts can rotate through rotary motors, the two pressing parts are arranged above the close ends of the two positioning clamps, the two butt joint mechanisms are connected with one ends of the two positioning clamps, and the power mechanism is in transmission connection with the two butt joint mechanisms. Two pre-welded base materials can be accurately in butt joint automatically, the problems that gaps are too large and the surfaces are not smooth after butt joint are completely eradicated, and therefore the following welding quality is improved.