The utility model relates to a last R round pin mounting tool of transmission line specifically is distal end R sells mounting tool. The problem of can't adopt the manual mode to carry out the operation of R round pin remounting at the distal end of indisputable tower end's jumbo size gold utensil is solved. This instrument comprises cavity insulator spindle and the feeding pole that inserts the cavity insulator spindle, the one end of cavity insulator spindle is by the shutoff, and it has a gap to go up to open in the shutoff part, and the central line in gap and the coincidence of the central line of cavity insulator spindle, the width of the R lock ring end when its opening end of the length more than or equal to in gap is closed, the width in gap are greater than the thickness of R round pin, and puts into the gap inwards when the ring end that the R round pin corresponds length direction, the R round pin in gap with width direction and rotate 90 when spending again, and the opening end ability compressed closure that R sells is between the width in gap. The utility model relates to a rationally, convenient to use is swift, has both avoided the safe risk of intermediate potential operation, has satisfied again and has overhauld in the operation needs of ultra -high voltage transmission line great distance apart from the location installation of indisputable tower end R round pin.