The invention provides a precision shunt resistor and its producing method, and it is composed of a resistor body and a bus bar made of red copper plate, and it has the character: it adopts a manganin plate with a temperature coefficient less than 20ppm as the resistor body and there is a transition manganin-red copper alloy band with temperature coefficient less than 50ppm, formed by electronic beam welding and fusion, between the resistor and the bus bar. There are installation holes and a voltage end. It has the advantages of low temperature coefficient, high reliability, heavy current rating, small bulk, convenient use, etc. Its producing method has a few production procedures, and high production efficiency, convenient for automatic production and at the same time can effectively assure it has better thermal stability and very high reliability.